JP2019144410A - Fixing device and image forming apparatus - Google Patents

Abstract

To cause a sheet to stably enter between a heating member and a pressure member regardless of a type of the sheet.SOLUTION: A fixing device 13 comprises: a fixing roller 20; a pressure roller 21; a pre-entry guide 24 that guides a non-image surface side of a sheet; an opposing guide 25 that guides an image surface side of the sheet; and a moving mechanism 23 that moves the pressure roller 21 to adjust a pressure applied by the pressure roller 21 according to a type of the sheet. The pre-entry guide 24 is configured to move in conjunction with movement of the pressure roller 21 caused by the moving mechanism 23; the pre-entry guide 24 is arranged so that the sheet is conveyed through the pre-entry guide 24 and opposing guide 25 in order to adjust the pressure applied by the pressure roller 21 to a normal first applied pressure, and the pre-entry guide 24 is arranged so that the sheet is conveyed through the pre-entry guide 24 without passing through the opposing guide 25 in order to adjust the pressure applied by the pressure roller 21 to a second applied pressure weaker than the first applied pressure.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device that fixes a toner image on a sheet, and an image forming apparatus including the fixing device.

  Conventionally, an image forming apparatus includes a fixing device that fixes a toner image formed on a recording medium such as paper. The fixing device includes a heating member that heats the toner image and a pressure member that pressurizes the toner image against the recording medium.

  For example, a fixing device of an image forming apparatus disclosed in Patent Document 1 includes an entrance guide for guiding a transfer material to a fixing nip, and the entrance guide is provided with an operable protrusion. When a transfer material whose length in the sheet passing direction is longer than a certain length is passed, the projecting portion is disposed at a position above the plane of the entrance guide. On the other hand, when a transfer material whose length in the paper passing direction is a certain length or less is passed, the protrusion is disposed below the plane of the entrance guide.

JP 2003-84595 A

  A sheet (for example, an end thereof) is wavy due to water absorption, or curled due to double-sided printing or backing paper printing. In the fixing device, the paper that has been wavy or curled tends to become unstable between the heating member and the pressure member, and when such a paper is subjected to a fixing process, the paper is likely to be wrinkled. Examples of paper used in the fixing device include plain paper and thin paper that are likely to be wrinkled, thick paper that is prone to image defects due to a conveyance load caused by collision and rubbing with a guide member, a heating member, and a pressure member. There is an envelope. The fixing device includes a guide member such as the above-described entrance guide in order to stabilize the paper entering between the heating member and the pressure member. However, although the above entrance guide depends on the length of the paper, it does not consider the thickness or material of the paper that is the source of wrinkles or image defects, and also considers reducing the transport load. Absent.

  In view of the above circumstances, an object of the present invention is to allow a sheet to stably enter between a heating member and a pressure member regardless of the type of sheet.

  The fixing device according to the present invention includes a heating member that heats a toner image formed on a sheet, a pressure member that pressurizes the sheet that is pressed against the heating member and passes between the heating member, A first guide member for guiding a non-image surface side of the paper conveyed between the heating member and the pressure member; and an image of the paper conveyed between the heating member and the pressure member. A second guide member for guiding the surface side, and a moving mechanism for moving the pressure member with respect to the heating member so as to adjust the pressing force of the pressure member according to the type of the paper, The first guide member is configured to move in conjunction with the movement of the pressurizing member by the moving mechanism, and when adjusting the pressurizing force of the pressurizing member to a normal first pressurizing force The paper is carried via the first guide member and the second guide member. When the first guide member is arranged and the pressure force of the pressure member is adjusted to a second pressure force that is weaker than the first pressure force, the sheet passes through the second guide member. The first guide member is disposed so as to be conveyed via the first guide member without being performed.

  The second guide member is configured to move in conjunction with the movement of the pressurizing member by the moving mechanism, and when adjusting the pressurizing force of the pressurizing member to the first pressurizing force, When the second guide member is disposed so that the sheet is conveyed via the first guide member and the second guide member, and the pressing force of the pressing member is adjusted to the second pressing force. The second guide member may be arranged so that the sheet is conveyed via the first guide member without passing through the second guide member.

  The second guide member is provided in the vicinity of the heating member, the first guide member is provided on the upstream side of the second guide member in the paper transport direction, and the pressing force of the pressure member is In the case of the first pressurizing force, the first guide member is arranged to guide the paper to the second guide member, and the second guide member is configured to guide the paper to the heating member and the pressure member. When the pressing force of the pressing member is the second pressing force, the first guiding member guides the paper between the heating member and the pressing member. The second guide member may be arranged so as to move away from the sheet conveyance path.

  In the fixing device described above, when the pressing force of the pressing member is the first pressing force, the heating member and the pressing member are rotationally driven at a normal first conveying speed, and the pressing force of the pressing member is In the case of the second applied pressure, the heating member and the pressure member may be rotationally driven at a second transport speed that is slower than the first transport speed.

  The image forming apparatus of the present invention includes the above-described fixing device.

  According to the present invention, regardless of the type of paper, the paper can be stably entered between the heating member and the pressure member.

1 is a cross-sectional view illustrating a printer according to an embodiment of the present invention. FIG. 3 is a cross-sectional view illustrating the fixing device when the applied pressure is a first applied pressure in the printer according to the embodiment of the present disclosure. FIG. 6 is a cross-sectional view illustrating the fixing device when the applied pressure is a second applied pressure in the printer according to the embodiment of the present disclosure. 1 is a block diagram illustrating an electrical configuration of a fixing device of a printer according to an embodiment of the present invention. 6 is a flowchart illustrating an operation of a fixing device of a printer according to another embodiment of the present invention. It is sectional drawing which shows the fixing device of the printer which concerns on other embodiment of this invention.

  First, the overall configuration of a printer 1 (image forming apparatus) according to an embodiment of the present invention will be described with reference to FIG. Hereinafter, for convenience of explanation, the front side of the sheet in FIG. Arrows L, R, U, and Lo appropriately attached to the drawings indicate the left side, right side, upper side, and lower side of the printer 1, respectively.

  The printer 1 includes a substantially box-shaped printer main body 2. A paper feed cassette 3 for storing paper (recording medium) is provided at a lower portion of the printer main body 2. A paper discharge tray 4 is provided at the upper portion of the printer main body 2. Provided.

  An exposure unit 5 composed of a laser scanning unit (LSU) is disposed on the left side of the printer body 2, and an image forming unit 6 is provided on the right side of the printer body 2. The image forming unit 6 is rotatably provided with a photosensitive drum 7 as an image carrier. Around the photosensitive drum 7, a charging device, a developing device connected to a toner container, a transfer roller 12a, and the like are provided. The cleaning device is disposed along the rotation direction of the photosensitive drum 7.

  A paper transport path 10 is provided on the right side of the printer main body 2 from below to above. A paper feed unit 11 is provided in the vicinity of the paper feed cassette 3 at the upstream end of the transport path 10, and a transfer unit 12 including a photosensitive drum 7 and a transfer roller 12 a is provided in the middle part of the transport path 10. . A fixing device 13 is provided in the downstream portion of the transport path 10, and a paper discharge unit 14 is provided in the vicinity of the paper discharge tray 4 at the downstream end of the transport path 10. Further, a control device 15 that controls the fixing process of the fixing device 13 is provided in the printer main body 2.

  Next, an image forming operation of the printer 1 having such a configuration will be described. The printer 1 starts an image forming operation when image data is input from an external computer or the like and an instruction to start printing is given. First, after the surface of the photosensitive drum 7 is charged by the charging device of the image forming unit 6, the photosensitive drum 7 is exposed according to the image data by the laser beam from the exposure device 5, and the photosensitive drum. An electrostatic latent image is formed on the surface 7. Next, the electrostatic latent image is developed into a toner image by the developer of the image forming unit 6 using toner.

  On the other hand, the paper stored in the paper feed cassette 3 is taken out by the paper feed unit 11 and transported on the transport path 10. The sheet on the conveyance path 10 is conveyed to the transfer unit 12 at a predetermined timing, and the toner image on the photosensitive drum 7 is transferred to the sheet by the transfer unit 12. The sheet on which the toner image has been transferred is conveyed to the fixing device 13 and the toner image is fixed on the sheet by the fixing device 13. The paper on which the toner image is fixed is discharged from the paper discharge unit 14 to the paper discharge tray 4.

  Next, the configuration of the fixing device 13 will be described with reference to FIGS. As shown in FIGS. 2 and 3, the fixing device 13 includes a fixing roller 20 (heating member), a pressure roller 21 (pressure member), a heat source 22, a moving mechanism 23, and a pre-entry guide 24 (first guide). 1 guide member) and an opposing guide 25 (second guide member).

  Each part of the fixing device 13 is attached to a substantially box-shaped fixing frame (not shown), and the fixing frame is arranged so that the conveyance path 10 penetrates the fixing frame in the paper conveyance direction (vertical direction). 2 is attached. In the fixing frame, the fixing roller 20 and the pressure roller 21 are disposed on the left side and the right side, respectively, with the conveyance path 10 interposed therebetween, and are disposed to face each other and to be in contact with each other. A pressure region N is formed in the transport path 10 between the fixing roller 20 and the pressure roller 21. The pressure area N is an area where the fixing roller 20 and the pressure roller 21 are in contact with each other, and is from the upstream position in the transport direction where the pressure applied to the paper by the fixing roller 20 and the pressure roller 21 is 0 Pa. The region from the position in the transport direction where the pressure is maximum to the downstream position in the transport direction where the pressure becomes 0 Pa again is shown.

  The fixing roller 20 is configured by a cylindrical roller that is long in the width direction (front-rear direction) of the paper, which is orthogonal to (crosses) the paper conveyance direction (up-down direction). The fixing roller 20 includes, for example, a cylindrical metal core material and an elastic layer made of a resin such as silicon rubber provided around the core material. The elastic layer is covered with a release layer with a fluorine-based resin. The The fixing roller 20 is rotatably attached to the frame with the front-rear direction as the rotation axis direction, and rotates following the rotation of the pressure roller 21. In this embodiment, an example in which the heating member is configured by the fixing roller 20 will be described, but the heating member may be configured by a belt.

  Inside the fixing roller 20, a heat source 22 for heating the fixing roller 20 over the width direction of the paper is provided. The heat source 22 is controlled by the control device 15 to switch heating on and off. The fixing roller 20 is heated by the heat source 22 and contacts the paper on which the toner image is formed to heat the toner image. The heat source 22 is composed of, for example, a halogen heater or a ceramic heater. Alternatively, the heat source 22 may be provided outside the fixing roller 20 and configured to heat the fixing roller 20 from the outside, and is not limited to a halogen heater or a ceramic heater, and may be an IH heater.

  The pressure roller 21 is formed in a substantially cylindrical shape that is long in the paper width direction (front-rear direction). The pressure roller 21 is composed of, for example, a cylindrical metal core material 21a and an elastic layer made of resin such as silicon rubber provided around the core material 21a. The elastic layer is a release layer made of a fluororesin. Is covered.

  The pressure roller 21 is attached to the fixing frame so as to be rotatable around a rotation axis extending in the front-rear direction. That is, the rotation axis direction of the pressure roller 21 is the front-rear direction. For example, a drive gear (not shown) is fixed to the rear end portion of the pressure roller 21, and the pressure roller 21 is connected to a roller drive source 26 (see FIG. 4) such as a motor through the drive gear. The roller drive source 26 is rotationally driven. The pressure roller 21 presses the paper passing through the pressure region N together with the fixing roller 20. For example, when the paper is plain paper or thin paper, the roller drive source 26 adjusts the paper conveyance speed by the pressure roller 21 to a normal first conveyance speed (for example, 190 mm / s or 150 mm / s), When the paper is an envelope, a cardboard, or the like, the transport speed is adjusted to a second transport speed that is weaker than the first transport speed (for example, half speed or 3/4 speed of the first transport speed).

  The moving mechanism 23 includes a pair of holding plates 30, a pair of pressure plates 31, a pair of pressure springs 32, a pair of guide springs 33, a pair of pressure cams 34, and a camshaft 35. The pair of holding plates 30, the pair of pressure plates 31, the pair of pressure springs 32, the pair of guide springs 33, and the pair of pressure cams 34 are respectively disposed on both ends in the axial direction of the pressure roller 21 and are symmetric. It has a typical configuration.

  Each holding plate 30 is formed in an elongated shape in the vertical direction, and a shaft support portion 30 a is provided on the upper portion of each holding plate 30. The shaft support portion 30 a supports the end portion of the core material 21 a serving as the rotation shaft of the pressure roller 21. A rail 30b that slidably supports the pre-entry guide 24 extends in the vertical direction at the lower portion of each holding plate 30. Each holding plate 30 is disposed on the right side of the fixing roller 20, is movable in the left-right direction, and is attached to the fixing frame so as to be swingable around the core member 21a. For example, the shaft support portion 30 a is recessed on the surface (left surface) of each holding plate 30 facing the fixing roller 20.

  Each pressure plate 31 is formed to have a plate body 31a that is long in the vertical direction, and an extension 31b that extends from the lower portion of the plate body 31a to each holding plate 30 side (left side). Each pressure plate 31 is disposed on the right side of each holding plate 30 and is attached to the fixing frame so as to be movable in the left-right direction. The upper ends of the plate bodies 31 a of the pressure plates 31 are connected to the upper ends of the holding plates 30 via the pressure springs 32. The extension portions 31 b of the pressure plates 31 are connected to the pre-entry guides 24 attached to the holding plates 30 via the guide springs 33. A protrusion 31c is formed at the end of each extension plate 31b on the side of each holding plate 30 (left side). For example, the protrusion 31 c is formed in a rectangular shape when viewed from the front, and engages with the guide 24 before entering, thereby restricting movement of the guide 24 before entering along the rail 30 b of each holding plate 30. Moreover, each holding plate 30 side (left side) end surface of the extension part 31b may be formed to be inclined to the lower right side.

  Each of the pressure springs 32 is disposed above the pressure roller 21 between each of the holding plates 30 and each of the pressure plates 31, and in a direction (left-right direction) separating each of the holding plates 30 and each of the pressure plates 31. Energize. Each guide spring 33 is disposed between each pressure plate 31 and the pre-entry guide 24, and biases the pre-entry guide 24 in a direction to draw it toward each pressurization plate 31.

  Each pressure cam 34 is disposed on the opposite side of each holding plate 30 (on the right side of the pressure plate 31) with each pressure plate 31 interposed therebetween, and is fixed to both ends of a cam shaft 35 extending in the axial direction of the pressure roller 21. Is done. An end (for example, rear end) of the camshaft 35 is connected to a cam drive source 36 (see FIG. 4) such as a motor, and the camshaft 35 is rotated by a rotational drive force from the cam drive source 36. In response to the rotation of the camshaft 35, each pressure cam 34 also rotates. Each pressurization cam 34 is constituted by, for example, a plate cam whose peripheral surface is in contact with each pressurization plate 31, and moves each pressurization plate 31 in the left-right direction according to rotation.

  According to the moving mechanism 23, the cam shaft 35 and the pressure cams 34 are rotated by the cam drive source 36, and the pressure plates 31 are pressed toward the holding plates 30 by the pressure cams 34. Each pressure plate 31 presses each pressure spring 32 toward each holding plate 30, and each pressure spring 32 receives a load from each pressure plate 31 and directs each holding plate 30 toward the fixing roller 20. Press. As a result, the pressure roller 21 held on each holding plate 30 moves to the fixing roller 20 side, and the pressure roller 21 is pressed against the fixing roller 20.

  As described above, the moving mechanism 23 can adjust the pressure applied to the fixing roller 20 by the pressure roller 21 according to the driving force of the cam drive source 36 and the rotation amounts of the cam shaft 35 and the pressure cams 34. For example, when the paper is plain paper or thin paper, the pressure is adjusted to the normal first pressure (for example, 130 N ± 5%), and when the paper is envelope or cardboard, the first pressure is applied. It adjusts to the 2nd pressurizing force (for example, 60N +/- 5%) weaker than a pressure. The pressure increases as the pressure roller 21 approaches the fixing roller 20. The first pressurization position P1 in the left-right direction of the pressure roller 21 where the applied pressure becomes the first applied pressure (see FIG. 2) is the second applied pressure in the left-right direction of the pressure roller 21 where the applied pressure becomes the second applied pressure. It is closer to the fixing roller 20 than the pressure position P2 (see FIG. 3).

  The pre-entry guide 24 is provided upstream of the fixing roller 20 and the pressure roller 21 in the transport direction of the transport path 10, and guides the paper transported on the transport path 10 to the pressure region N. The pre-entry guide 24 is disposed on the pressure roller 21 side with respect to the transport path 10 and guides the non-image surface (non-image forming surface) side of the paper. The pre-entry guide 24 may have a paper guide surface 24a in the axial direction of the pressure roller 21, or may have a guide surface 24a at predetermined intervals in the axial direction. For example, the pre-entry guide 24 includes a guide body 24b and a protrusion 24c that protrudes from the guide body 24b to the upper left side, and the protrusion 24c forms a guide surface 24a that curves from the lower right side to the upper left side. . The guide body 24b of the pre-entry guide 24 is slidably attached to the rail 30b of each holding plate 30, and the pre-entry guide 24 moves on the rail 30b in conjunction with the movement of the pressure roller 21 by the moving mechanism 23. To do.

  The opposing guide 25 is provided upstream of the fixing roller 20 and the pressure roller 21 in the conveyance direction of the conveyance path 10, and guides the sheet conveyed on the conveyance path 10 to the pressure region N. The opposing guide 25 is disposed on the fixing roller 20 side with respect to the conveyance path 10 and guides the image surface (image forming surface) side of the sheet. The opposing guide 25 may have a paper guide surface 25a along the axial direction of the fixing roller 20, or may have a guide surface 25a at predetermined intervals in the axial direction. The opposing guide 25 is attached to the fixing frame so as to be rotatable around the rotation shaft 25 b, and rotates (moves) in conjunction with the movement of the pressure roller 21 by the moving mechanism 23. The opposing guide 25 may include a drive source (not shown) different from the cam drive source 36 in order to rotate the rotating shaft 25 b in conjunction with the movement of the pressure roller 21, or the cam drive source 36. May be provided with a gear mechanism that transmits the rotational driving force to the rotary shaft 25b, or a power conversion mechanism that is interlocked with the movement of each pressure plate 31 or each holding plate 30. Note that the opposing guide 25 is disposed in the vicinity of the fixing roller 20, and the rotation shaft 25b is provided in the vicinity of the fixing roller 20, whereby the movement of the opposing guide 25 with respect to the conveyance path 10 can be increased.

  The movement of the pre-entry guide 24 and the opposing guide 25 in conjunction with the movement of the pressure roller 21 will be described. As the pre-entry guide 24 and the opposing guide 25 move, the paper transport path 10 changes as shown in FIGS. For example, as shown in FIG. 2, when the holding plates 30 and the pressure plates 31 of the moving mechanism 23 are arranged so as to adjust the pressure roller 21 to the first pressurizing force, the guide 24 before entering the The extension part 31b of each pressure plate 31 pressed to the plate 30 side is arranged at the lower part of the rail 30b, and the movement is restricted by the protrusion part 31c. The opposing guide 25 is fixed by rotating the guide surface 25 a to a position along the transport path 10.

  At this time, as shown in FIG. 2, the pre-entry guide 24 is disposed on the lower right side (upstream side in the transport direction) of the opposing guide 25, and the guide surface 24 a of the pre-entry guide 24 guides the paper to be transported. It arrange | positions so that it may guide to the guide surface 25a of the opposing guide 25. FIG. Then, the sheet is conveyed via the pre-entry guide 24 and the opposing guide 25 and enters the pressure region N while reducing undulation and curling.

  On the other hand, as shown in FIG. 3, when the holding plates 30 and the pressure plates 31 of the moving mechanism 23 are arranged so as to adjust the pressure roller 21 to the second pressurizing force, each pressure plate 31 corresponds to each holding plate. By moving to the side away from 30, the engagement of the pre-entry guide 24 by the protrusion 31c, that is, the movement restriction is released. Further, the pre-entry guide 24 is attracted by each guide spring 33 and moves to the upper portion of the rail 30b. The opposing guide 25 is fixed by rotating to a position where the guide surface 25 a is separated from the conveyance path 10.

  At this time, as shown in FIG. 3, each holding plate 30 is attracted by each pressure spring 32, swings around the core material 21 a, and the tip of the protruding portion 24 c of the pre-entry guide 24 is fixed to the fixing roller 20. And between the pressure rollers 21. Further, the pre-entry guide 24 is disposed in the vicinity of the pressure roller 21, and the guide surface 24 a of the pre-entry guide 24 is disposed along the transport path 10. Then, the sheet is transported via the pre-entry guide 24 without passing through the opposing guide 25 and directly enters the pressurizing region N along the pre-entry guide 24.

  Next, the electrical configuration of the control device 15 that controls the fixing device 13 will be described with reference to FIG. The control device 15 is composed of a CPU or the like, and is connected to a storage device 16 such as a ROM or a RAM. In addition, as the control device 15 and the storage device 16, a main control device and a main storage device that collectively control each unit of the printer 1 may be applied.

  The control device 15 controls each unit connected to the control device 15 based on a control program and control data stored in the storage device 16. For example, the control device 15 is connected to a roller drive source 26 of the pressure roller 21, a heat source 22, a cam drive source 36 of the cam shaft 35, and the like. The control device 15 controls the fixing process of the fixing device 13, and in particular, controls the movement of the pre-entry guide 24 and the opposing guide 25 that are linked to the movement of the pressure roller 21.

  Next, the operation of the fixing device 13 will be described with reference to FIG. First, the control device 15 of the fixing device 13 determines the type of paper conveyed to the fixing device 13 based on the print settings (step S1). Then, when the paper type is plain paper, thin paper, or the like (step S1: YES), the control device 15 controls the roller drive source 26 so that the paper transport speed by the pressure roller 21 becomes the first transport speed. At the same time (step S2), the cam drive source 36 of the moving mechanism 23 is controlled so that the pressure applied by the pressure roller 21 becomes the first pressure (step S3). At this time, the pre-entry guide 24 and the opposing guide 25 move as described above in conjunction with the movement of the pressure roller 21 by the moving mechanism 23 (see FIG. 2). On the other hand, the control device 15 controls the roller drive source 26 so that the paper transport speed by the pressure roller 21 becomes the second transport speed when the paper type is an envelope, thick paper, or the like (step S1: NO). (Step S4), the cam drive source 36 of the moving mechanism 23 is controlled so that the pressure applied by the pressure roller 21 becomes the second pressure (Step S5). Note that the pre-entry guide 24 and the opposing guide 25 move as described above in conjunction with the movement of the pressure roller 21 by the moving mechanism 23 (see FIG. 3). Then, after controlling the conveyance speed and the applied pressure, the process proceeds to the fixing process (step S6).

  According to the present embodiment, as described above, the fixing device 13 of the printer 1 (image forming apparatus) has a fixing roller 20 (heating member) that heats the toner image formed on the paper and the fixing roller 20. A pressure roller 21 (pressure member) that pressurizes the paper that is pressed and passes between the fixing roller 20 and a non-image surface side of the paper that is conveyed between the fixing roller 20 and the pressure roller 21. A pre-advance guide 24 (first guide member) for guiding, an opposing guide 25 (second guide member) for guiding the image surface side of the sheet conveyed between the fixing roller 20 and the pressure roller 21; A moving mechanism 23 that moves the pressure roller 21 relative to the fixing roller 20 so as to adjust the pressure applied to the pressure roller 21 according to the type. The pre-entry guide 24 is configured to move in conjunction with the movement of the pressure roller 21 by the moving mechanism 23, and when adjusting the pressure of the pressure roller 21 to the normal first pressure, When the pre-entry guide 24 is arranged so that the paper is conveyed via the pre-entry guide 24 and the opposing guide 25, and the pressing force of the pressure roller 21 is adjusted to a second pressing force that is weaker than the first pressing force. In this case, the pre-entry guide 24 is arranged so that the sheet is conveyed via the pre-entry guide 24 without passing through the opposing guide 25.

  Further, the opposing guide 25 is configured to move in conjunction with the movement of the pressure roller 21 by the movement mechanism 23, and when adjusting the pressure of the pressure roller 21 to the first pressure, the paper When the opposed guide 25 is disposed so that the pressure is conveyed through the pre-advance guide 24 and the opposed guide 25 and the pressing force of the pressure roller 21 is adjusted to the second applied pressure, the sheet moves the facing guide 25. The opposing guide 25 is arranged so as to be conveyed via the pre-entry guide 24 without going through.

  According to the above configuration, when the fixing device 13 operates with the normal first pressurizing force, each side of the paper is not moved into the front side even when paper such as plain paper or thin paper that is likely to be wrinkled is conveyed. It is conveyed along the guide 24 and the opposing guide 25. For this reason, the amount of contact of the paper with the guide increases, and after the waving and curling generated on the paper are reduced, the paper enters the pressure region N while being in contact with the fixing roller 20. Thereby, the wrinkle of the paper after passing the fixing roller 20 and the pressure roller 21 can be suppressed. On the other hand, when operating with a second pressure that is weaker than the first pressure, the image tends to be defective due to a transport load caused by a collision or rubbing with the pre-entry guide 24, the opposing guide 25, the fixing roller 20, and the pressure roller 21. Even if paper such as cardboard or envelope is transported, the paper is transported along the pre-entry guide 24 and is transported directly toward the pressure region N while being in contact with the fixing roller 20. Therefore, collision and rubbing between the sheet and the pre-entry guide 24 and the opposed guide 25 can be minimized without the pre-entry guide 24 and the opposed guide 25 interfering with the sheet conveyance path 10. Accordingly, it is possible to suppress the image conveyance failure by suppressing the sheet conveyance load.

  In the fixing device 13, the opposing guide 25 is provided in the vicinity of the fixing roller 20, and the pre-entry guide 24 is provided upstream of the opposing guide 25 in the sheet transport direction. When the pressing force of the pressure roller 21 is the first pressing force, the pre-entry guide 24 is arranged to guide the paper to the opposing guide 25, and the opposing guide 25 is configured to guide the paper to the fixing roller 20, the pressure roller 21, and the like. It arrange | positions so that it may guide between. When the pressure force of the pressure roller 21 is the second pressure force, the pre-entry guide 24 is arranged to guide the paper between the fixing roller 20 and the pressure roller 21, and the opposing guide 25 is a paper transporter. It moves to the side away from the path 10 and is arranged. As a result, when operating with a normal first pressure, the amount of contact of the paper with the guide is increased with a simple configuration, and when operating with a second pressure that is weaker than the first pressure, Collisions and rubbing with the pre-entry guide 24 and the opposing guide 25 can be suppressed with a simple configuration.

  In the fixing device 13, when the pressing force of the pressure roller 21 is the first pressing force, the fixing roller 20 and the pressing roller 21 are rotationally driven at a normal first conveyance speed, and the pressing force of the pressing roller 21 is changed. In the case of the second applied pressure, the fixing roller 20 and the pressure roller 21 are rotationally driven at a second transport speed that is slower than the first transport speed. As a result, even when the pressure roller 21 is set to a lower second pressure, the paper is passed between the fixing roller 20 and the pressure roller 21 at a slower second conveyance speed. Can be sufficiently reduced.

  In the above-described embodiment, the example in which the extension portion 31b of the pre-entry guide 24 is provided with the protruding portion 31c at the end of each holding plate 30 (left side) has been described, but the configuration of the pre-entry guide 24 is not limited thereto. . For example, as shown in FIG. 6, the extension 31 b of the pre-entry guide 24 has an inclined surface that is inclined from the upper left end to the lower right, and the upper left end engages with the pre-entry guide 24. It may be configured to.

  In the above-described embodiment, the example in which each guide spring 33 is disposed between each pressure plate 31 and the pre-entry guide 24 has been described. However, the configuration of each guide spring 33 is not limited thereto. For example, each guide spring 33 may be disposed between each holding plate 30 and the pre-entry guide 24. Even in the configuration in which the pre-entry guide 24 is pulled up from the upper side (see FIG. 6), the pre-entry guide 24 from the lower side. It is also possible to push up.

  In the present embodiment, the case where the configuration of the present invention is applied to the monochrome printer 1 has been described. However, in another different embodiment, the present invention is applied to other image forming apparatuses such as a color printer, a copier, a facsimile machine, and a multifunction machine. It is also possible to apply this configuration.

1 Printer (image forming device)
6 Image Forming Unit 7 Photosensitive Drum 10 Conveyance Path 12 Transfer Unit 13 Fixing Device 14 Paper Discharging Unit 15 Control Device 16 Storage Device 20 Fixing Roller (Heating Member)
21 Pressure roller (pressure member)
21a Core material 22 Heat source 23 Movement mechanism 24 Pre-entry guide (first guide member)
24a Guide surface 24b Guide body 24c Protruding portion 25 Opposing guide (second guide member)
25a Guide surface 25b Rotating shaft 26 Roller drive source 30 Holding plate 30a Shaft support 30b Rail 31 Pressure plate 31a Plate body 31b Extension portion 31c Projection portion 32 Pressure spring 33 Guide spring 34 Pressure cam 35 Camshaft 36 Cam drive source

Claims (5)

A heating member for heating the toner image formed on the paper;
A pressing member that pressurizes the paper that is pressurized against the heating member and passes between the heating member;
A first guide member for guiding a non-image surface side of the paper conveyed between the heating member and the pressure member;
A second guide member for guiding an image surface side of the sheet conveyed between the heating member and the pressure member;
A moving mechanism that moves the pressure member relative to the heating member so as to adjust the pressure applied to the pressure member according to the type of the paper,
The first guide member is configured to move in conjunction with the movement of the pressure member by the moving mechanism,
When adjusting the pressing force of the pressurizing member to a normal first pressing force, the first guide member is moved so that the sheet is conveyed via the first guide member and the second guide member. Arranged,
When adjusting the pressing force of the pressurizing member to a second pressing force that is weaker than the first pressing force, the sheet is conveyed via the first guide member without passing through the second guide member. The fixing device is characterized in that the first guide member is arranged as described above. The second guide member is configured to move in conjunction with the movement of the pressure member by the moving mechanism,
When adjusting the pressing force of the pressurizing member to the first pressing force, the second guide member is arranged so that the sheet is conveyed via the first guide member and the second guide member. And
When adjusting the pressing force of the pressurizing member to the second pressing force, the second sheet is conveyed so that the sheet is conveyed via the first guide member without passing through the second guide member. The fixing device according to claim 1, wherein a guide member is disposed. The second guide member is provided in the vicinity of the heating member,
The first guide member is provided on the upstream side of the second guide member in the transport direction of the paper,
When the pressurizing force of the pressurizing member is the first pressurizing force, the first guide member is arranged to guide the paper to the second guide member, and the second guide member guides the paper to the second pressurizing member. Arranged to guide between the heating member and the pressure member,
When the pressing force of the pressing member is the second pressing force, the first guide member is disposed so as to guide the paper between the heating member and the pressing member, and the second guide member The fixing device according to claim 1, wherein the fixing device is arranged so as to move away from the sheet conveyance path. When the pressurizing force of the pressurizing member is the first pressurizing force, the heating member and the pressurizing member are rotationally driven at a normal first transport speed,
4. When the pressing force of the pressing member is the second pressing force, the heating member and the pressing member are rotationally driven at a second transport speed slower than the first transport speed. The fixing device described.   An image forming apparatus comprising the fixing device according to claim 1.

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