Heating and conveying device and image forming apparatus

Abstract

To prevent a large curl from occurring in a sheet ejected from an ejection port.SOLUTION: A fixing device 20 is provided, which comprises a fixing belt 21 (fixing rotating body) that is heated by a planar heater 24 (heating means), and a pressure roller 31 (pressure rotating body) that is in pressure contact with the fixing belt 21 to form a nip part through which a sheet P is conveyed. A conveyance guide plate 110 (conveyance guide member) is provided, which guides the sheet P sent out from the nip part of the fixing device 20 toward an ejection port A. When seen in a cross section orthogonal to a width direction, the direction of the sheet P sent out from an exit N2 of the nip part is on the opposite side of a side where the ejection port A is located, with respect to a virtual vertical straight line H passing through the exit N2 of the nip part in the fixing device 20.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a heating and conveying device that heats and conveys a sheet, and to an image forming apparatus including the heating and conveying device, such as a copying machine, a printer, a facsimile machine, or a combination machine thereof. [Background technology]

[0002] Conventionally, in image forming devices such as copiers and printers, a conveying guide member (conveying guide plate) is used to guide a sheet sent out from a fixing device toward an outlet while bending the sheet in a predetermined direction, and the sheet is then discharged from the device through the outlet (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0003] With conventional devices, sheets discharged from the discharge port tended to curl significantly, resulting in poor appearance and stackability.

[0004] The present invention has been made to solve the above-mentioned problems, and aims to provide a heating and conveying device and an image forming device in which a sheet discharged from a discharge port is less likely to curl significantly. [Means for solving the problem]

[0005] The heating and conveying device of this invention comprises a fixing device having a fixing rotor heated by a heating means, a pressure rotor that forms a nip portion through which a sheet is conveyed by being pressed against the fixing rotor, and a conveying guide member that guides the sheet sent out from the nip portion of the fixing device toward an outlet, and when viewed in a cross section perpendicular to the width direction, the orientation of the sheet sent out from the outlet of the nip portion in the fixing device is opposite the side on which the outlet is located, with respect to an imaginary vertical line passing through the outlet of the nip portion in the fixing device. [Effects of the Invention]

[0006] According to the present invention, it is possible to provide a heating and conveying device and an image forming apparatus in which a sheet discharged from a discharge port is less likely to curl significantly. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is an overall configuration diagram showing an image forming apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram illustrating a configuration of a fixing device. [Figure 3] FIG. 2 is a top view of the fixing device as viewed in the width direction. [Figure 4] FIG. 2 is a schematic side view showing the fixing belt and the guide member in the width direction. [Figure 5] FIG. 2 is a view showing the plane heater in the width direction. [Figure 6] FIG. 2 is a cross-sectional view showing a thermostat. [Figure 7] FIG. [Figure 8] FIG. 10 is an enlarged view showing a heating and conveying device as a comparative example. [Figure 9] 6 is a timing chart showing control of the fixing device at the start of printing. [Figure 10] 10 is a flowchart illustrating an example of control performed in the image forming apparatus. [Figure 11] FIG. 10 is an enlarged view showing a fixing device according to a first modified example. [Figure 12] FIG. 10 is an enlarged view showing a heating and conveying device as a second modified example. [Figure 13] FIG. 10 is an enlarged view showing a heating and conveying device as a third modified example. [Figure 14] FIG. 10 is a structural diagram showing a fixing device according to a fourth modified example. [Figure 15] FIG. 13 is a structural diagram showing a fixing device according to a fifth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be appropriately simplified or omitted.

[0009] First, the overall configuration and operation of an image forming apparatus 1 will be described with reference to FIG. 1, the image forming apparatus 1 in this embodiment is a tandem color printer. Four toner bottles 102Y, 102M, 102C, and 102K corresponding to the respective colors (yellow, magenta, cyan, and black) are detachably (replaceably) installed in a bottle storage section 101 located at the top of the image forming apparatus main body 1. An intermediate transfer unit 85 is disposed below the bottle storage section 101. Opposite to the intermediate transfer belt 78 of the intermediate transfer unit 85, image forming sections 4Y, 4M, 4C, and 4K corresponding to each color (yellow, magenta, cyan, and black) are arranged side by side.

[0010] Each of the image forming units 4Y, 4M, 4C, and 4K is provided with a photosensitive drum 5Y, 5M, 5C, and 5K, respectively. A charging unit 75, a developing unit 76, a cleaning unit 77, a charge removal unit, and the like are disposed around each of the photosensitive drums 5Y, 5M, 5C, and 5K. The image forming apparatus 1 is equipped with a control unit 60. The control unit 60 controls various components to perform image forming processes (charging process, exposure process, development process, transfer process, and cleaning process) on the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K, thereby forming an image of each color on the surface of each of the photosensitive drums 5Y, 5M, 5C, and 5K.

[0011] The photosensitive drums 5Y, 5M, 5C, and 5K are rotated by a motor in the clockwise direction in Fig. 1. Then, at the position of the charging unit 75, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged (charging process). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser light L emitted from the exposure unit 3, and an electrostatic latent image corresponding to each color is formed by exposure scanning at this position (this is the exposure process).

[0012] Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach positions facing the developing unit 76, where the electrostatic latent images are developed to form toner images of the respective colors (developing step). Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach positions facing the intermediate transfer belt 78 and first transfer bias rollers 79Y, 79M, 79C, and 79K, and at these positions the toner images on the photosensitive drums 5Y, 5M, 5C, and 5K are transferred onto the intermediate transfer belt 78 (this is the primary transfer step). At this time, a small amount of untransferred toner remains on the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K.

[0013] Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning unit 77, at which point the untransferred toner remaining on the photosensitive drums 5Y, 5M, 5C, and 5K is mechanically collected by the cleaning blade of the cleaning unit 77 (cleaning process). Finally, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach positions facing the charge removal units, where the residual potential on the photosensitive drums 5Y, 5M, 5C, and 5K is removed. Thus, a series of image forming processes performed on the photosensitive drums 5Y, 5M, 5C, and 5K is completed.

[0014] Thereafter, the toner images of each color formed on each photosensitive drum through the development process are transferred in a superimposed manner onto the surface of the intermediate transfer belt 78. In this way, a color image is formed on the intermediate transfer belt 78. Here, the intermediate transfer unit 85 is composed of the intermediate transfer belt 78, four primary transfer bias rollers 79Y, 79M, 79C, and 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer cleaning section 80. The intermediate transfer belt 78 is stretched and supported by three rollers 82 to 84, and is moved endlessly in the direction of the arrow in FIG. 1 by the rotational drive of one roller 82.

[0015] The four primary transfer bias rollers 79Y, 79M, 79C, and 79K sandwich the intermediate transfer belt 78 between themselves and the photosensitive drums 5Y, 5M, 5C, and 5K, respectively, to form primary transfer nips. A transfer bias opposite in polarity to the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K. The intermediate transfer belt 78 then travels in the direction of the arrow and passes through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K in sequence. In this way, the toner images of each color on the photosensitive drums 5Y, 5M, 5C, and 5K are primarily transferred onto the intermediate transfer belt 78 in a superimposed manner.

[0016] Thereafter, the intermediate transfer belt 78, onto which the toner images of each color have been transferred and superimposed, reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between itself and the secondary transfer roller 89, forming a secondary transfer nip. The four-color toner images formed on the intermediate transfer belt 78 are then transferred onto the sheet P that has been transported to the position of this secondary transfer nip. At this time, untransferred toner that has not been transferred to the sheet P remains on the intermediate transfer belt 78. Thereafter, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning unit 80. At this position, untransferred toner on the intermediate transfer belt 78 is collected. Thus, the series of transfer processes performed on the intermediate transfer belt 78 is completed.

[0017] Here, the sheet P transported to the position of the secondary transfer nip is transported from the feeding section 12 arranged below the image forming apparatus main body 1 via a transport path arranged on the side of the image forming apparatus main body 1 (on which a paper feed roller 97, a pair of registration rollers 98, a fixing device 20, a transport guide plate 110, etc. are arranged). More specifically, a plurality of sheets P such as paper are stacked and stored in the feeding section 12. When the paper feed roller 97 is rotated counterclockwise in FIG. 1, the topmost sheet P is fed toward between the pair of registration rollers 98.

[0018] The sheet P conveyed to the registration roller pair 98 stops temporarily at the roller nip position of the registration roller pair 98, which has stopped rotating. Then, the registration roller pair 98 is rotated in synchronization with the color image on the intermediate transfer belt 78, and the sheet P is conveyed toward the secondary transfer nip. In this way, the desired color image is transferred onto the sheet P.

[0019] Thereafter, the sheet P onto which the color image has been transferred at the secondary transfer nip position is conveyed to the position of the fixing device 20. Then, at this position, the color image transferred onto the surface is fixed onto the sheet P by the heat and pressure of the fixing belt 21 and the pressure roller 31 (fixing process). Then, the sheet P sent out from the fixing device 20 is guided by a conveying guide plate 110 serving as a conveying guide member and conveyed toward the discharge outlet A. Then, the sheet P is discharged from the discharge outlet A to the outside of the device by a pair of discharge rollers 99. The sheets P discharged from the discharge outlet A by the pair of discharge rollers 99 are sequentially stacked on a stack unit 100 as output images. In this way, a series of image forming processes (printing operations) in the image forming apparatus is completed. In this embodiment, the fixing device 20 and the transport guide plate 110 (transport guide member) constitute a heating transport device 19 that heats and transports the sheet P, which will be described in detail later.

[0020] In this way, in the image forming apparatus 1 of this embodiment, the sheet transport path from the feeding section 12 to the discharge outlet A is located on one side of the image forming apparatus main body 1 (the right side in Figure 1), forming an approximately C-shaped transport path. By forming such a substantially C-shaped conveying path, the conveyance and discharge of the sheet P are stabilized.

[0021] Next, the configuration and operation of the fixing device 20 installed in the image forming apparatus main body 1 will be described in detail with reference to FIGS. The fixing device 20 is a device that conveys the sheet P (a sheet carrying unfixed toner T) while heating it. 2 to 4, the fixing device 20 is composed of a fixing belt 21 as a fixing rotor, a reinforcing member 30, a planar heater 24 as a heating means (heating body), a pressure roller 31 as a pressure rotor, a thermostat 40 (bimetal thermostat), and the like.

[0022] Here, the fixing belt 21 is an endless belt member that contacts the outside of the pressure roller 31 and rotates in accordance with the rotation of the pressure roller 31. The fixing belt 21 is a thin, flexible endless belt that rotates (rotates in a driven manner) in the direction of the arrow (counterclockwise) in Fig. 2. The fixing belt 21 has a base layer, an elastic layer, and a release layer laminated in this order from the inner circumferential surface (the surface that comes into contact with the planar heater 24), and the overall thickness is set to 1 mm or less. The base material layer of the fixing belt 21 has a thickness of 30 to 50 μm and is made of a metal material such as nickel or stainless steel, or a resin material such as polyimide. The elastic layer of the fixing belt 21 has a thickness of 100 to 300 μm and is made of a rubber material such as silicone rubber, foamed silicone rubber, fluororubber, etc. By providing the elastic layer, minute irregularities are prevented from being formed on the surface of the fixing belt 21 at the fixing nip, and heat is transferred uniformly to the toner image T on the sheet P, preventing the occurrence of an orange peel image. The release layer of the fixing belt 21 has a layer thickness of 5 to 50 μm and is made of a material such as PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES (polyethersulfone), etc. Providing the release layer ensures releasability (separability) for the toner T (toner image).

[0023] On the inside (inner peripheral surface side) of the fixing belt 21, a sheet heater 24, a holder 23, a reinforcing member 30, a thermostat 40, etc. are provided. Here, the sheet heater 24 is disposed so as to extend in the width direction (the direction perpendicular to the plane of FIG. 2, the left-right direction in FIGS. 3 and 4, and the up-down direction in FIG. 5). The sheet heater 24 is in pressure contact with the pressure roller 31 via the fixing belt 21 on the inside (inner peripheral surface side) of the fixing belt 21, forming a nip portion (fixing nip) through which the sheet P is conveyed. That is, the sheet heater 24 is disposed so as to be in sliding contact with the inner peripheral surface of the fixing belt 21. The sheet heater 24 is in pressure contact with the pressure roller 31 via the fixing belt 21, thereby forming a nip portion through which the sheet P is conveyed. In this way, the sheet heater 24 functions as a member (nip portion-forming member) that forms the nip portion (fixing nip). Note that, in order to reduce sliding resistance with the fixing belt 21, the surface of the sheet heater 24 may be covered with a sheet-like member or provided with a surface layer made of a low-friction material such as PTFE. Furthermore, a resistor pattern 26 (see FIG. 5, etc.) is formed on the portion of the planar heater 24 that comes into sliding contact with the inner circumferential surface of the fixing belt 21. Electric power is supplied to the resistor pattern 26 (heating resistor) from a power supply unit (not shown), and the resistor pattern 26 generates heat due to its resistance, thereby heating the fixing belt 21. In this way, the planar heater 24 also functions as a heating means (heating element) that heats the fixing belt 21. In this embodiment, the nip portion in the fixing device 20 is configured to be flat, but the nip portion can also be configured to be curved (for example, concave to match the curvature of the pressure roller 31).

[0024] In this embodiment, the planar heater 24 is held by a holder 23 (holding member). The holder 23 has a recess formed therein, and the sheet heater 24 is fitted into the recess, thereby holding the sheet heater 24 across the width. The holder 23 is held by the reinforcing member 30 while holding the planar heater 24. The reinforcing member 30 holding the planar heater 24 and the holder 23 has both widthwise ends held by the housing 43 of the fixing device 20 via flange members 42 (see FIG. 3, etc.).

[0025] In this way, the fixing belt 21 is directly heated by the planar heater 24 (resistor pattern 26) installed inside the fixing belt 21. Then, heat is applied to the toner image T on the sheet P from the surface of the heated fixing belt 21. Here, the output control of the planar heater 24 is performed based on the temperature detection results by a thermostat 40 that is in direct contact (or indirectly via another member) with the planar heater 24. In this embodiment, no temperature sensor is provided that directly detects the surface temperature of the fixing belt 21, and the surface temperature (fixing temperature) of the fixing belt 21 is indirectly controlled to a desired temperature by controlling the temperature of the planar heater 24 by the thermostat 40. The configurations and operations of the sheet heater 24 and the thermostat 40 will be described in more detail later with reference to FIGS.

[0026] Referring to FIG. 4, the pair of flange members 42 guide both widthwise ends of the fixing belt 21 from the inner peripheral surface side so that the fixing belt 21 is maintained in a substantially cylindrical position. More specifically, the two flange members 42 are made of a heat-resistant resin material or the like, and are held so as to be slidable in a direction to form a nip portion (fixing nip) at both widthwise ends of the housing 43 of the fixing device 20. The flange members 42 are provided with a guide portion 42a for holding the fixing belt 21 while maintaining the substantially cylindrical posture of the fixing belt 21, a stopper portion for restricting movement of the fixing belt 21 in the widthwise direction (toward the belt), and the like. In addition, in this embodiment, as shown in Figure 3, the fixing belt 21 (and the planar heater 24 and holder 23) is configured to be pressed against the pressure roller 31 by pressure applied by the pressure lever 52 (pressure mechanism 51) via the flange member 42. The flange members 42 are arranged at both ends in the width direction within a circumferential range excluding the fixing nip so as not to interfere with the formation of the fixing nip by the planar heater 24 . Furthermore, in this embodiment, the only members that come into contact with the inner circumferential surface of the fixing belt 21 are the flange members 42 that come into loose contact at both ends in the width direction, and the planar heater 24; there are no other members (belt guides) that come into contact with the inner circumferential surface and guide the rotation of the fixing belt 21.

[0027] In this embodiment, the reinforcing member 30 is installed inside the fixing belt 21 so as to contact the pressure roller 31 via the planar heater 24 (and the holder 23) and the fixing belt 21. The reinforcing member 30 reinforces the strength of the planar heater 24 (and the holder 23) that form the fixing nip, and is installed on the holder 23 (or the housing 43) by screw fastening or the like. The reinforcing member 30 contacts the pressure roller 31 via the planar heater 24 (and holder 23) and the fixing belt 21, thereby preventing the planar heater 24 (and holder 23) from being significantly deformed in the fixing nip due to the pressure of the pressure roller 31. To fulfill the above-mentioned functions, the reinforcing member 30 is preferably made of a metal material with high mechanical strength, such as stainless steel or iron.

[0028] The holder 23 may be made of a resin material or a metal material, but is preferably made of a resin material (such as liquid crystal polymer (LCP), polyamideimide (PAI), polyethersulfone (PES), polyphenylene sulfide (PPS), polyethernitrile (PEN), polyetheretherketone (PEEK), etc.) that is rigid enough not to bend significantly even when subjected to the pressure of the pressure roller 31 and has thermal and heat insulating properties. In this embodiment, the holder 23 is made of a liquid crystal polymer (LCP).

[0029] Referring to Figure 2, the pressure roller 31 as a pressure rotating body has an elastic layer 33 provided on a core metal 32 (shaft portion), and is driven to rotate in a predetermined direction (clockwise in Figure 2) by a drive motor 95. The core metal 32 of the pressure roller 31 is a hollow structure made of a metal material. The elastic layer 33 of the pressure roller 31 is made of a material such as foamed silicone rubber, silicone rubber, or fluororubber. A thin release layer made of PFA, PTFE, or the like may be provided on the surface of the elastic layer 33. The pressure roller 31 presses against the fixing belt 21 to form a desired fixing nip between the two members. Referring to FIG. 3, the pressure roller 31 is provided with a gear 45 that meshes with the drive gear of the drive motor 95, and the pressure roller 31 is driven to rotate in the direction of the arrow in FIG. 2 (clockwise). Both widthwise ends of the pressure roller 31 are rotatably supported by a housing 43 of the fixing device 20 via bearings.

[0030] The normal operation of the fixing device 20 configured as described above will now be briefly described. When the power switch of the device main body 1 is turned on, power is supplied to the planar heater 24, and the pressure roller 31 starts to rotate in the direction of the arrow in Fig. 2. As a result, the frictional force with the pressure roller 31 at the fixing nip causes the fixing belt 21 to rotate (co-rotate) in the direction of the arrow in Fig. 2. Thereafter, the sheet P is fed from the feeding section 12, and an unfixed color image is carried (transferred) onto the sheet P at the position of the secondary transfer roller 89. The sheet P carrying the unfixed image (toner image) is conveyed in the direction of arrow Y10 in FIG. 2 while being guided by a guide plate, and is sent into the fixing nip between the fixing belt 21 and pressure roller 31, which are in a pressure-contact state. The toner image is fixed onto the surface of the sheet P by heating from the fixing belt 21 heated by the planar heater 24 and by the pressing force of the planar heater 24 (and the holder 23) reinforced by the reinforcing member 30 and the pressure roller 31. Thereafter, the sheet P sent out from the fixing nip is transported in the direction of the arrow Y11.

[0031] Referring to Figure 5, the planar heater 24 in this embodiment is formed of a substrate 25 (base portion), a resistor pattern 26 (heating resistor), a conductor pattern 27 (relay portion), a power supply electrode 28 as an electrode, and the like. At least the front surface (the surface facing the inner circumferential surface of the fixing belt 21 in the nip portion) of the base material 25 is made of an insulating material. In this embodiment, the base material 25 is entirely made of an insulating material (in this embodiment, aluminum nitride (AIN)). The resistor pattern 26 is formed on the front surface of the substrate 25. Similarly, the conductor pattern 27 is also formed on the front surface of the substrate 25. The resistor pattern 26 functions as a heating resistor that generates heat due to the resistance when a current flows through it (is energized). The resistor pattern 26 is formed by applying a paste prepared to have a desired resistance value to the surface of the substrate 25 by screen printing or the like, and then baking the applied paste to form a pattern. The conductor pattern 27 is electrically connected to the resistor pattern 26 (and the power supply electrode 28), and functions as a relay section that passes the current input from the power supply electrode 28 to the resistor pattern 26. The conductor pattern 27 is formed by applying a paste made of a highly conductive material to the surface of the substrate 25 by screen printing or the like, and then baking the paste to form a pattern. The power supply electrode 28 is electrically connected to the conductor pattern 27 and is formed so as to be connectable to a connector (not shown) that serves as an external terminal. Therefore, even if a surface layer having insulating properties and low friction is formed over the entire surface of the sheet heater 24, only the power supply electrode 28 will be exposed from the surface layer so as to be able to supply power. Power supply electrode 28 is made of a silver-based material such as silver (Ag) or silver palladium (AgPd) in order to reduce heat generation due to current flow. In this embodiment, power supply electrode 28 is formed by printing on the surface of substrate 25 by screen printing and then baking.

[0032] Also, referring to Figure 6 etc., thermostat 40 in this embodiment is a bimetal thermostat, and is composed of cap 401, bimetal 402, pin 403, first contact 404, second contact 405, spring 406, terminal 407, mounting fixture 408, case 409, etc. In bimetal thermostat 40, when the temperature of bimetal 402, which receives heat from cap 401 in contact with sheet heater 24 (resistor pattern 26), which is the object, exceeds a predetermined temperature, bimetal 402 deforms and presses pin 403. When pin 403 is pressed in this manner, first contact 404 and second contact 405, which are normally in contact due to the biasing force of spring 406, become separated, and the current flow via terminal 407 is released, and this released state causes control unit 60 to determine that sheet heater 24 has overheated. In this way, the thermostat 40 also functions as a safety device that prevents the temperature of the plane heater 24 from rising too high. It should be noted that the length of the pin 403 is set to a length that does not press the bimetal 402, since the temperature at which the bimetal 402 deforms changes when a mechanical force is applied. In addition, in this embodiment, the thermostats 40 are installed in three locations, namely, the central portion in the width direction and both end portions in the width direction, but the number and installation locations are not limited to this.

[0033] Also, referring to FIG. 5, the fixing device 20 in this embodiment is provided with a heat equalizing member 48 that comes into contact with the planar heater 24 to equalize the heat generated in the planar heater 24 (particularly, to equalize it in the width direction). The heat equalizing member 48 may be a sheet-like member made of a highly thermally conductive material such as metal or carbon. By installing such a heat equalizing member 48, when a sheet P having a widthwise size smaller than the widthwise length M (heat generation width) of the planar heater 24 (resistor pattern 26) is conveyed, it is possible to reduce the problem of the heater temperature rising in the area (non-paper passing area) where the sheet P does not pass, causing temperature unevenness in the widthwise direction. Therefore, it is also possible to reduce curl (curl in the widthwise direction) that occurs in the sheet P after the fixing process due to such temperature unevenness.

[0034] The characteristic configuration and operation of the heating and conveying device 19 (image forming apparatus 1) in this embodiment will be described in detail below. The heating and conveying device 19 in this embodiment is a device that heats and conveys the sheet P, and is mainly composed of a fixing device 20 and a conveying guide plate 110 as a conveying guide member. As previously explained using Figure 2 etc., the fixing device 20 is provided with a planar heater 24 as a heating means extending in the width direction, a fixing belt 21 as a fixing rotor heated by the planar heater 24, a pressure roller 31 as a pressure rotor that forms a nip portion (fixing nip) by being pressed against the planar heater 24 via the fixing belt 21, and a thermostat 40 that is in direct or indirect contact with the planar heater 24.

[0035] Now, referring to Figure 7 (and Figure 1), the heating and conveying device 19 (image forming device 1) in this embodiment is provided with a conveying guide plate 110, which is a conveying guide member that guides the sheet P sent out from the nip portion (fixing nip) of the fixing device 20 toward the discharge outlet A and serves as a correction member that corrects curls in the sheet P. Specifically, the conveying guide plates 110 (conveying guide members) are provided in pairs downstream of the fixing device 20 and upstream of the discharge outlet A (discharge roller pair 99) so as to face the front side (the side facing the fixing belt 21 when passing through the nip portion of the fixing device 20) and the back side (the side facing the pressure roller 31 when passing through the nip portion of the fixing device 20) of the conveyed sheet P, respectively. Furthermore, the conveying guide plates 110 form a sheet conveying path that bends (or curves) from the lower right side to the upper left side in FIG. 7 (and FIG. 1), and guide the sheet P after the fixing process toward the discharge outlet A while curving it (curving in a direction that follows the bending or curving direction of the conveying guide plates 110). The shape of the transport guide plate 110 is not limited to that shown in FIG. 7, and for example, it may be formed of only a curved guide plate, or may be formed of only a flat guide plate.

[0036] As shown in Figure 7, when viewed in a cross section perpendicular to the width direction, the image forming apparatus 1 in this embodiment is configured so that the direction (virtual line S) of the sheet P sent out from the outlet N2 of the nip portion (fixing nip) in the fixing device 20 is on the opposite side to the side where the discharge outlet A is located (the right side in Figure 7) with respect to the virtual vertical line H passing through the outlet N2 of the nip portion (fixing nip). Specifically, fixing device 20 is configured such that fixing belt 21 (fixing rotor) is disposed closer to discharge outlet A (left side in FIG. 7) than pressure roller 31 (pressure rotor), and sheet P is sent obliquely upward from the nip portion (fixing nip) (in the direction of imaginary line S connecting entrance N1 and exit N2 of the nip portion). Also, when viewed in a cross section perpendicular to the width direction, imaginary line S is inclined away from discharge outlet A with respect to imaginary vertical line H extending vertically. In other words, exit N2 of the nip portion is located above a horizontal line passing through the center of pressure roller 31, and the direction of the nip portion near exit N2 is from the lower left to the upper right. In this specification, this virtual straight line S is defined as simply connecting the entrance N1 and exit N2 of the nip portion, even if the nip portion in the fixing device 20 is not formed flat but is formed curved (for example, if it is formed concavely to follow the curvature of the pressure roller 31).

[0037] The conveying guide plate 110 extends downstream from near the exit N2 of the nip portion approximately parallel to the imaginary line S, and then extends downstream toward the discharge outlet A so as to be inclined at an angle θ (contact angle) with the imaginary line S. That is, the imaginary line S passing through the entrance N1 and exit N2 of the nip portion in Fig. 7 is inclined diagonally upward to the right compared to the imaginary line S' (an imaginary vertical line extending vertically upward) in fixing device 200 shown in Fig. 8 as a comparative example. Therefore, the angle θ1 (contact angle) formed by the intersection of conveying guide plate 110 and imaginary line S in Fig. 7 is smaller than the angle θ1 in Fig. 7 and the angle θ' (contact angle) shown in Fig. 8 as a comparative example (θ1<θ').

[0038] Here, the sheet P sent out from the nip portion (fixing nip) curls (curves) so that the back surface shrinks as moisture evaporates from the back side (non-fixed surface side) in the process of cooling from a high temperature state. However, immediately after being sent out from the nip portion (fixing nip), the sheet P collides with the conveying guide plate 110 at a relatively shallow angle θ1 (contact angle) (while the sheet P is still hot), and the back surface of the sheet P is conveyed along the conveying guide plate 110 while making contact with it. The sheet P is conveyed along the conveying guide member 110 while bending at the position where it collides with the conveying guide plate 110, so that the sheet P is finally discharged from the discharge port A in a state where the curl has been straightened. In particular, the image forming apparatus 1 in this embodiment has a substantially C-shaped conveying path as described above, and can install the conveying guide plate 110 which makes it easy to straighten the curl, making the configuration in this embodiment useful. Therefore, the sheets P discharged from the discharge port A and stacked in the stacking unit 100 have reduced curl (curvature), resulting in good appearance and stackability.

[0039] After being conveyed along the conveying guide plate 110, the sheet P is discharged while being nipped by the discharge roller pair 99, but it may also be discharged while being pulled between the discharge roller pair 99 and the fixing nip (nip portion). For example, by setting the rotation speed of the discharge roller pair 99 faster than the speed of the sheet P sent out from the exit N2 of the nip portion, the sheet P can be discharged while being pulled between the discharge roller pair 99 and the fixing nip (nip portion). For example, the heating and conveying device 19 (image forming device 1) in this embodiment may be provided with a correction section 110a as a correction member that corrects the sending direction (conveying direction) of the sheet P sent out from the exit N2 of the nip section (fixing nip) to the direction in which the discharge outlet A is located. The correcting portion 110a is a part of the conveying guide plate 110 (conveying guide member), and is a portion that faces the front surface (fixing surface) of the sheet P, extends downstream from near the exit N2 of the nip portion, and is bent at a predetermined angle. The straightening section 110a can bend the sheet P sent out from the outlet N2 of the nip section in the range of 90 to 100 degrees toward the discharge outlet A. With this configuration, it is possible to further reduce curl (curvature) of the sheet P after it has been conveyed along the conveying guide plate 110. In this embodiment, a part of the conveying guide plate 110 (conveying guide member) is used as the correction member, but a separate member (for example, a square-claw-shaped member formed to protrude toward the conveying path) that imparts a reverse curl to the sheet P immediately after it is sent out from the nip portion can also be installed as the correction member. Furthermore, when the correction unit 110a is configured with a rotating body, the image on the front surface (fixing surface) of the sheet P is less likely to be scratched.

[0040] Referring now to FIG. 7, thermostat 40 is disposed so as to face pressure roller 31 (pressure rotating body) with planar heater 24 interposed therebetween. Specifically, the thermostat 40 is disposed at an angle relative to the vertical direction together with the sheet heater 24. The thermostat 40 applies pressure to the sheet heater 24 in the direction of the white arrow that is substantially perpendicular to the imaginary line S (a direction that is inclined diagonally downward relative to the horizontal direction), and is pressed against the pressure roller 31 via the sheet heater 24. Therefore, unlike fixing device 200 shown in Fig. 8 as a comparative example in which thermostat 40 and sheet heater 24 are arranged vertically, a gravity component acts on bimetal 402 (see Fig. 6) of thermostat 40 in a direction approaching (contacting) cap 401 (see Fig. 6). Therefore, even if bimetal 402 is held loosely in case 409 of sheet heater 24, the gravity component described above makes it easier for bimetal 402 to come into contact with cap 401, and false detection (a decrease in detection accuracy for detecting excessive temperature rise of sheet heater 24) caused by a gap (floating) being formed between cap 401 and bimetal 402 can be prevented. Therefore, it is possible to accurately detect an excessive temperature rise (heat source runaway) of the planar heater 24 and cut off the power supply to the planar heater 24 at an appropriate timing based on the detection result.

[0041] Furthermore, in the fixing device 20, as previously explained using Figure 2 etc., the surface temperature (fixing temperature) of the fixing belt 21 is indirectly controlled by controlling the temperature of the planar heater 24 using the thermostat 40. That is, in this embodiment, the fixing temperature is not directly controlled based on the detection result of a temperature sensor that directly detects the surface temperature of the fixing belt 21, but is indirectly controlled based on the detection result of the thermostat 40. Specifically, when the temperature of the planar heater 24 detected by the thermostat 40 is higher than the predetermined range, it is determined that the fixing temperature of the fixing belt 21 is higher than the predetermined temperature range, and power supply to the planar heater 24 is cut off. On the other hand, when the temperature of the planar heater 24 detected by the thermostat 40 is lower than the predetermined range, it is determined that the fixing temperature of the fixing belt 21 is lower than the predetermined temperature range, and power supply to the planar heater 24 is continued. In order to reduce curling that occurs in the sheet P after the fixing process, it is effective to keep the surface temperature (fixing temperature) of the fixing belt 21 as low as possible with good responsiveness. In this embodiment, as explained above, the contact angle θ between the virtual straight line S and the conveying guide plate 110 is set large, making curling less likely to occur (easier to correct), so even if the responsiveness of the temperature control is slow, by indirectly controlling the fixing temperature based on the detection results of the thermostat 40, the amount of curling that occurs can be sufficiently offset. In this embodiment, since no temperature sensor is provided to directly detect the surface temperature of the fixing belt 21, the cost of the fixing device 20 is reduced. In addition, instead of control using the thermostat 40 as described above, the temperature of the planar heater 24 may be detected by a temperature sensor, and the control unit 60 may control the power supply to the planar heater 24 based on the detection result of the temperature sensor.

[0042] 7 and other figures, fixing device 20 in this embodiment is configured so that the outer diameter of pressure roller 31 (pressure rotating member) is smaller than the outer diameter of fixing belt 21 (fixing rotating member). In this way, by reducing the outer diameter of the pressure roller 31 as a pressure rotating body, the heat capacity of the pressure roller 31 is reduced, resulting in energy saving of the fixing device 20. Furthermore, by reducing the diameter of the pressure roller 31, the fixing device 20 can be made smaller and less expensive. On the other hand, if the nip width is small, the curl that occurs in the sheet P after the fixing process will become large. However, in this embodiment, as explained above, the contact angle θ between the virtual straight line S and the conveying guide plate 110 is set large, making it difficult for curl to occur (because it is easy to correct), so even if the nip width is set small, the amount of curl that occurs can be sufficiently offset.

[0043] Also, referring to FIG. 9, the fixing device 20 in this embodiment is controlled so that heating of the fixing belt 21 by the planar heater 24 (heating means) begins without rotating the fixing belt 21 (fixing rotor) and the pressure roller 31 (pressure rotor) before the printing operation is started. More specifically, when a user operates a personal computer or the like connected to image forming apparatus 1 to send a print command to control unit 60 of image forming apparatus 1, this triggers the supply of power to planar heater 24, which starts heating fixing belt 21 (warming-up state). At this time, drive motor 95 (see FIG. 2) that drives pressure roller 31 to rotate is not driven, and fixing belt 21 and pressure roller 31 are in a stopped state, so that pressure roller 31 does not actively receive heat from fixing belt 21 in the circumferential direction. Then, when sheet P is actually fed from feed unit 12 and the printing operation (fixing process) starts, driving of drive motor 95 starts. By controlling in this manner, the driving time of the drive motor 95 can be reduced compared to when the drive motor 95 is started during warm-up using a print command as a trigger, which results in energy savings for the device and a shorter recovery time. On the other hand, if the drive motor 95 is not started during warm-up, the pressure roller 31 will not be sufficiently heated in the circumferential direction during the fixing process, and the curl that occurs in the sheet P after the fixing process will become large. However, in this embodiment, as explained above, the contact angle θ between the virtual straight line S and the conveying guide plate 110 is set large, making it difficult for curl to occur (because it is easy to correct), so even if the drive motor 95 is not started during warm-up, the amount of curl that occurs can be sufficiently offset.

[0044] Also, referring to Figure 10, in this embodiment, when sheets P (for example, small-sized sheets P less than A4 portrait size) whose width size is shorter than the width length M (see Figure 5) of the planar heater 24 (resistor pattern 26) as a heating means by a predetermined value or more are continuously transported, the number of sheets P transported (number of printed sheets) per unit time is controlled to be less than when sheets P of other width sizes (for example, sheets P larger than A4 portrait size) are continuously transported. That is, when a small-sized sheet P having a widthwise size sufficiently small relative to the widthwise length M of the planar heater 24 (resistor pattern 26) is transported, a low-speed printing mode is executed which is slower than the normal printing mode (normal printing mode). This is because, even when small-sized sheets P are continuously printed, if the normal printing mode is executed, the fixing temperature in the non-paper passing area at the nip (fixing nip) is more likely to rise than in the paper passing area, making it more likely that the sheet P will curl after the fixing process. In this embodiment, when small-sized sheets P are continuously printed, the number of sheets P transported (number of printed sheets) per unit time is reduced compared to the normal printing mode, which buys time for heat to transfer from the non-paper passing area to the paper passing area, making it less likely that the sheet P will curl after the fixing process. 10, when a print command is sent to the control unit 60, it is determined whether the width direction size of the sheet P is equal to or less than a predetermined value W based on the sheet information input by the user (step S1). If the width direction size of the sheet P is not equal to or less than the predetermined value W, the normal print mode is executed (step S2). On the other hand, if the width direction size of the sheet P is equal to or less than the predetermined value W, the low-speed print mode is executed (step S3).

[0045] <Variation 1> As shown in FIG. 11, in the fixing device 20 of the first modified example, the holder 23 holding the planar heater 24 is formed so that the outlet N2 side protrudes toward the pressure roller 31 (pressure rotating body) compared to the inlet N1 side. Specifically, when viewed in a cross section perpendicular to the width direction, the holder 23 in variant example 1 has a concave portion into which the approximately plate-shaped planar heater 24 fits, but the protrusion of the protruding portion 23a toward the pressure roller 31 on the entrance N2 side is longer than the protruding portion toward the pressure roller 31 on the entrance N1 side. By configuring it in this manner, the sheet P sent out from the nip portion is subjected to curl correction forces at two points: the exit N2 of the nip portion and the conveying guide plate 110, thereby further reducing the curl that occurs in the sheet P discharged from the discharge outlet A. The direction of the arrow in which the sheet P is sent from the outlet N2 of the nip portion is the same as the direction of the imaginary line S in FIG.

[0046] <Variation 2> As shown in FIG. 12, a transport guide plate 110 (transport guide member) in the second modification is configured so that the angle θ1 of inclination toward the discharge port A side is adjustable. In detail, the conveying guide plate 110 (the guide plate of the pair of guide plates that the sheet P sent out from the nip portion collides with) is configured to be rotatable around a rotation axis by a moving mechanism 120 consisting of a motor mechanism or the like. Then, the control unit 60 (see FIG. 1) determines whether the basis weight of the sheet P input by the user (or the basis weight of the sheet P included in the print data) is equal to or greater than a predetermined value Z (in other words, whether the sheet P is thick paper). When the control unit 60 determines that the basis weight of the sheet P to be conveyed is equal to or greater than the predetermined value Z (in other words, the sheet P is thick paper), the control unit 60 controls the movement mechanism 120 to adjust the angle θ1 (contact angle) formed by the conveying guide plate 110 so that it is larger than the angle θ1 when a sheet P with a basis weight less than the predetermined value Z (for example, regular paper or thin paper) is conveyed. Specifically, when a sheet P thinner than cardboard is conveyed, the conveying guide plate 110 is rotated by the movement mechanism 120 so that the contact angle becomes θ1 (the position indicated by the solid line in FIG. 12). On the other hand, when a sheet P as cardboard is conveyed, the conveying guide plate 110 is rotated by the movement mechanism 120 so that the contact angle becomes larger than θ1 (the position indicated by the dashed line in FIG. 12). The cardboard sheet P collides with the conveying guide plate 110 and is bent in the opposite direction to the curl caused by evaporation of water from the back surface of the sheet P. In other words, the cardboard sheet P is bent so that the center of the front surface, where the toner image is fixed, is depressed and the edges are raised. If the amount of deformation caused by the conveying guide plate 110 is too large, when the cardboard sheet P is discharged from the discharge port A, there is a possibility that the center of the front surface will be depressed and curled. According to the second modification, it is possible to reduce the occurrence of such curling. Furthermore, for stiff cardboard, by setting the contact angle to be larger than θ1, it is possible to correct curls and prevent conveyance problems.

[0047] <Variation 3> 13, the image forming apparatus 1 in Modification 3 is configured to be able to discharge a sheet P sent out from the nip portion to either a first discharge outlet A or a second discharge outlet B. The angle θ2 formed between a second transport guide plate 130 (second transport guide member) of the second discharge outlet B and an imaginary line S is larger than the angle θ1 formed between a first transport guide plate 110 (first transport guide member) of the first discharge outlet A and the imaginary line S (θ2>θ1). In addition, the second transport guide plate 130 as the second transport member is tilted more clockwise in FIG. 13 than the first transport guide plate 110 as the first transport member. More specifically, the first transport guide plate 110 is provided with a movable guide plate 111 as a switching portion between the first transport guide plate 110 and the second transport guide plate 130, which is rotatable around a support shaft 111a by being driven. When a sheet P (for example, plain paper or thin paper) having a basis weight less than a predetermined value Z is conveyed, the sheet P sent out from the nip portion is guided by the first conveying guide plate 110 and is discharged to the outside of the device from the first discharge port A. At this time, the movable guide plate 111 rotates to the dashed line position in FIG. 13, and a contact angle θ (<θ1) is formed with the correction portion 110a of the first conveying guide plate 110. On the other hand, when a sheet P (for example, cardboard) having a basis weight equal to or greater than a predetermined value Z is conveyed, the sheet P sent out from the nip portion is guided by the second conveying guide plate 130 and discharged from the second discharge outlet B to the outside of the apparatus. At this time, the movable guide plate 111 serving as a switching unit rotates to the position indicated by the solid line in FIG. 13 to switch to a conveying path that guides the sheet P toward the first discharge outlet A. At this time, the angle formed by the movable guide plate 111 at the position indicated by the dashed line in FIG. 13 and the imaginary line S is θ1. Then, after the back surface of the sheet P sent out from the nip portion collides with the movable guide plate 111 at the position indicated by the dashed line, the sheet P is conveyed while contacting the first conveying guide plate 110. At this time, the sheet P is conveyed along the first conveying guide plate 110 while bending at the position where it collides with the movable guide plate 111, thereby reducing curling. On the other hand, when a sheet P (for example, cardboard) having a basis weight equal to or greater than a predetermined value Z is conveyed, the sheet P sent out from the nip portion is guided by the second conveying guide plate 130 and is discharged to the outside of the device through the second discharge outlet B. At this time, the movable guide plate 111 serving as a switching portion rotates to the position shown by the solid line in FIG. 13 and switches to a conveying path that guides the sheet P toward the second discharge outlet B using the second conveying guide plate 130. At this time, the angle formed by the second conveying guide plate 130 and the virtual line S is θ2 (θ2>θ1). When the sheet P is conveyed as thick paper, by discharging the sheet P from the second discharge port B, which has a larger contact angle than the first discharge port A, it is possible to correct curls and prevent conveyance problems.

[0048] <Variation 4> As shown in FIG. 14, the fixing device 20 in the fourth modification is of a heater-roller type, in which a fixing roller 22 is used as a fixing rotor, and a halogen heater 35 is used as heating means. In detail, the fixing roller 22 (pressure body) as a fixing rotating body is a roller member with a multi-layer structure in which a coating layer (an elastic layer and a release layer laminated together) is formed on a hollow core metal made of a metal material such as stainless steel, and is pressed against the pressure roller 31 (pressurized body) as a pressure rotating body to form a fixing nip. The elastic layer in the covering layer 21b of the fixing roller 22 is made of an elastic material such as fluororubber, silicone rubber, foamed silicone rubber, etc. The release layer in the covering layer 21b of the fixing roller 22 is made of PFA (tetrafluoroethylene perfluoroalkylvinylether copolymer resin) or the like. A halogen heater 35 is fixedly provided inside (hollow portion of) the fixing roller 22 as a heating means. The fixing device 20 configured as described above operates as follows. When the main switch of the apparatus main body 1 is turned on, an AC voltage is applied (power is supplied) to the halogen heater 35 from the power supply of the image forming apparatus main body 1. When a print command (print request) is input, the drive motor (drive mechanism) starts rotating the fixing roller 22 clockwise, and the pressure roller 31 starts rotating counterclockwise. Thereafter, the sheet P is fed from the feed unit 12, and at the position of the transfer roller 9, the toner image on the photosensitive drum 1 is carried on the sheet P as an unfixed image. The sheet P carrying the unfixed image (toner image) is transported in the direction of the arrow in FIG. 14 and fed into a nip portion (fixing nip) between the fixing roller 22 and the pressure roller 31, which are in a pressure-contact state. The toner image is then fixed on the surface of the sheet P by the heat of the fixing roller 22 and the pressing force of the fixing roller 22 and the pressure roller 31. After the fixing process, the sheet P is sent out of the nip portion in the direction of the arrow by the rotating fixing roller 22 and pressure roller 31. 7, an image forming apparatus 1 equipped with a fixing device 20 configured in this manner is also provided with a conveying guide plate 110 (conveying guide member) that guides a sheet P sent out from a nip portion (fixing nip) of the fixing device 20 toward an outlet A while curving the sheet P in a predetermined direction. When viewed in a cross section perpendicular to the width direction, an imaginary straight line S extending in the conveying direction through an entrance N1 and an exit N2 of the nip portion (fixing nip) of the fixing device 20 is configured to be inclined away from the outlet A. This makes it difficult for a large curl to occur in the sheet P discharged from the outlet A.

[0049] <Variation 5> As shown in FIG. 15, the fixing device 20 in variant 5 is not one that uses a planar heater 24 or a heater heating method that uses a heater 35, but rather one that uses an electromagnetic induction method that uses an electromagnetic induction coil 50 that is installed opposite the outer surface of the fixing belt. More specifically, the fixing device 20 in the fifth modification is also provided with a nip forming member 37 (but not a planar heater) similar to that shown in FIG. Here, the fixing device 20 in the fifth modification is provided with an electromagnetic induction coil 50 (induction heating unit) as a heating means. The fixing belt 21 in the fifth modification is heated by electromagnetic induction by the electromagnetic induction coil 50. The electromagnetic induction coil 50 is integrally formed with a core, a coil guide, etc., and is made of a Litz wire, which is a bundle of thin wires, extended in the width direction so as to cover a portion of the fixing belt 21. The coil guide is made of a highly heat-resistant resin material or the like, and holds the electromagnetic induction coil 50 and the core. The core is a semi-cylindrical member made of a ferromagnetic material such as ferrite (with a relative magnetic permeability of approximately 1000 to 3000), and is provided with a center core and side cores to form an efficient magnetic flux toward the fixing belt 21. The core is disposed so as to face the electromagnetic induction coil 50 extended in the width direction. 2 and the like, a heat-generating layer (for example, it can be formed between the elastic layer and the release layer, or the base layer can be used as the heat-generating layer) that is electromagnetically induction heated by the electromagnetic induction coil 50 is formed on the fixing belt 21. The heat-generating layer can be made of nickel, stainless steel, iron, copper, cobalt, chromium, aluminum, gold, platinum, silver, tin, palladium, an alloy made of a plurality of these metals, or the like. The fixing device 20 configured in this manner operates as follows. 15, fixing belt 21 is heated at a position facing electromagnetic induction coil 50. More specifically, by passing a high-frequency alternating current through electromagnetic induction coil 50, magnetic field lines are formed around fixing belt 21 so that they alternate in both directions. At this time, eddy currents are generated on the surface of the heat-generating layer of fixing belt 21, and Joule heat is generated due to the electrical resistance of the heat-generating layer itself. This Joule heat electromagnetically heats the heat-generating layer, and fixing belt 21 is heated. In the example of FIG. 15, the electromagnetic induction coil 50 is disposed so as to face the outer peripheral surface of the fixing belt, but the electromagnetic induction coil 50 may also be disposed so as to face the inner peripheral surface of the fixing belt. 7, an image forming apparatus 1 equipped with an electromagnetic induction type fixing device 20 configured as above is also provided with a conveying guide plate 110 (conveying guide member) that guides a sheet P sent out from a nip portion (fixing nip) of the fixing device 20 toward an outlet A while curving the sheet P in a predetermined direction. When viewed in a cross section perpendicular to the width direction, an imaginary straight line S extending in the conveying direction through an entrance N1 and an exit N2 of the nip portion (fixing nip) of the fixing device 20 is configured to be inclined away from the outlet A. This makes it difficult for a large curl to occur in the sheet P discharged from the outlet A.

[0050] As described above, the heating and conveying device 19 (image forming apparatus 1) in this embodiment is provided with the fixing device 20, which includes the fixing belt 21 (fixing rotor) heated by the planar heater 24 (heating means) and the pressure roller 31 (pressure rotor) that presses against the fixing belt 21 to form a nip portion through which the sheet P is conveyed. The fixing device 20 is also provided with a conveying guide plate 110 (conveying guide member) that guides the sheet P delivered from the nip portion of the fixing device 20 toward the discharge outlet A. When viewed in a cross section perpendicular to the width direction, the sheet P delivered from the nip outlet N2 in the fixing device 20 is oriented opposite the discharge outlet A with respect to the imaginary vertical line H that passes through the nip outlet N2. This makes it difficult for the sheet P discharged from the discharge port A to curl significantly.

[0051] In this embodiment, the present invention is applied to an image forming apparatus 1 equipped with a fixing device 20 using a pressure roller 31 as a pressure rotating body. However, the present invention can also be applied to an image forming apparatus equipped with a fixing device using a pressure belt as a pressure rotating body. Furthermore, in this embodiment, a plate-shaped conveying guide plate 110 made of sheet metal or the like is used as the conveying guide member, but the conveying guide member is not limited to this as long as it has a guide surface capable of guiding a sheet, and for example, a non-plate-shaped member made of a thick resin material can also be used. In this embodiment, the present invention is applied to the image forming apparatus 1 in which the sheet P is transported vertically, but the present invention can also be applied to an image forming apparatus in which the sheet P is transported horizontally. In that case, when viewed in a cross section perpendicular to the width direction, the imaginary straight line S is configured to be inclined away from the discharge port with respect to an imaginary horizontal line extending vertically. Furthermore, in this embodiment, the present invention is applied to the heating and conveying device 19 installed in the image forming apparatus 1, but the heating and conveying device to which the present invention is applied is not limited to this, and the present invention can also be applied to, for example, a heating and conveying device installed in a drying device of an inkjet type image forming apparatus, or a heating and conveying device installed in a laminating device. In these cases, the same effect as that of this embodiment can be obtained.

[0052] It is to be noted that the present invention is not limited to the present embodiment, and it is clear that the present embodiment can be appropriately modified within the scope of the technical concept of the present invention in addition to the modifications suggested in the present embodiment. Furthermore, the number, position, shape, etc. of the components are not limited to the present embodiment, and the number, position, shape, etc. of the components can be any number, position, shape, etc. that is suitable for implementing the present invention. [Explanation of symbols]

[0053] 1 Image forming apparatus (image forming apparatus main body), 19 Heating conveying device, 20 Fixing device, 21 Fixing belt (fixing rotating body), 23 holder (holding member), 24 Planar heater (heating means), 31 pressure roller (pressure rotating body), 40 Thermostat (bimetal thermostat), 48 Heat equalizing element, 110 conveying guide plate (conveying guide member), 110a correction portion (correction member), 111 Movable guide plate (switching part), 130 second transport guide plate (second transport guide member), A outlet, B second outlet, S imaginary line, P sheet (recording medium).

[0054] The present invention can also be embodied in a combination of Supplementary Notes 1 to 11, for example, as follows. (Appendix 1) a fixing device including a fixing rotor heated by a heating means and a pressure rotor that is pressed against the fixing rotor to form a nip portion through which a sheet is conveyed; a conveyance guide member that guides the sheet sent out from the nip portion of the fixing device toward a discharge port; Equipped with A heating and conveying device characterized in that, when viewed in a cross section perpendicular to the width direction, the orientation of the sheet sent out from the outlet of the nip portion in the fixing device is on the opposite side to the side on which the discharge outlet is located, with respect to a virtual vertical line passing through the outlet of the nip portion in the fixing device. (Appendix 2) The heating and conveying device described in Appendix 1, characterized in that the conveying guide member is a correction member that corrects the sheet discharge direction of the sheet discharged from the exit of the nip portion toward the direction in which the discharge outlet is located. (Appendix 3) The heating and conveying device according to claim 2, wherein the correcting member is a part of the conveying guide member. (Appendix 4) the fixing device includes a plane heater as the heating means extending in the width direction, a fixing belt as the fixing rotor heated by the plane heater, the pressure rotor that forms the nip portion by being pressed against the plane heater via the fixing belt, and a thermostat that directly or indirectly contacts the plane heater; 4. The heating and conveying device according to any one of claims 1 to 3, wherein the thermostat is disposed so as to face the pressure rotating body across the plane heater. (Appendix 5) the fixing device includes a holder that holds the planar heater; 5. The heating and conveying device according to claim 4, wherein the holder is formed so that the outlet side protrudes toward the pressure rotating body. (Appendix 6) The heating and conveying device according to any one of Supplementary Note 1 to Supplementary Note 5, wherein the fixing device is configured so that the outer diameter of the pressure rotating body is smaller than the outer diameter of the fixing rotating body. (Appendix 7) the outlet comprises a first outlet and a second outlet; the conveying guide member includes a first conveying guide member that guides the sheet toward the first discharge opening and a second conveying guide member that guides the sheet toward the second discharge opening; A heating and conveying device as described in any one of Appendix 1 to Appendix 6, characterized in that the angle at which the sheet sent out from the nip portion collides with the first conveying guide member is different from the angle at which the sheet sent out from the nip portion collides with the second conveying guide member. (Appendix 8) The heating and conveying device described in Appendix 7 is characterized in that it is equipped with a switching unit that switches so that the sheet sent out from the nip portion is conveyed toward either the first conveying guide member or the second conveying guide member. (Appendix 9) The transport guide member is The angle of inclination toward the outlet side is adjustable, A heating and conveying device described in any one of Appendix 1 to Appendix 8, characterized in that when a sheet having a basis weight equal to or greater than a predetermined value is conveyed, the angle is adjusted to be larger than when a sheet having a basis weight less than the predetermined value is conveyed. (Appendix 10) The heating and conveying device according to any one of Supplementary Note 1 to Supplementary Note 9, wherein the fixing device is provided with a heat equalizing member that contacts the planar heater and equalizes the heat generated in the planar heater. (Appendix 11) An image forming apparatus comprising the heating and conveying device according to any one of Supplementary Notes 1 to 10. [Prior art documents] [Patent documents]

[0055] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-34079

Claims

1. a fixing device including a fixing rotor heated by a heating means and a pressure rotor that forms a nip portion through which a sheet is conveyed by being pressed against the fixing rotor; a conveyance guide member that guides the sheet sent out from the nip portion of the fixing device toward a discharge port; Equipped with A heating and conveying device characterized in that, when viewed in a cross section perpendicular to the width direction, the orientation of the sheet sent out from the outlet of the nip portion in the fixing device is on the opposite side to the side on which the discharge outlet is located, with respect to a virtual vertical line passing through the outlet of the nip portion in the fixing device.

2. 2. The heating and conveying device according to claim 1, wherein the conveying guide member is a correcting member that corrects the sheet sent out from the outlet of the nip portion in a direction toward the discharge port.

3. 3. The heating and conveying device according to claim 2, wherein the straightening member is a part of the conveying guide member.

4. the fixing device includes a plane heater as the heating means extending in the width direction, a fixing belt as the fixing rotor heated by the plane heater, the pressure rotor that forms the nip portion by being pressed against the plane heater via the fixing belt, and a thermostat that directly or indirectly contacts the plane heater; 2. The heating and conveying device according to claim 1, wherein the thermostat is disposed so as to face the pressure rotating body across the plane heater.

5. the fixing device includes a holder that holds the planar heater; 5. The heating and conveying device according to claim 4, wherein the holder is formed so that the outlet side protrudes toward the pressure rotating body.

6. 3. The heating and conveying device according to claim 1, wherein the fixing device is configured such that the outer diameter of the pressure rotating body is smaller than the outer diameter of the fixing rotating body.

7. the outlet comprises a first outlet and a second outlet; the transport guide member includes a first transport guide member that guides the sheet toward the first discharge opening and a second transport guide member that guides the sheet toward the second discharge opening; 3. The heating and conveying device according to claim 1, wherein the angle at which the sheet sent out from the nip portion collides with the first conveying guide member is different from the angle at which the sheet sent out from the nip portion collides with the second conveying guide member.

8. The heating and conveying device according to claim 7, further comprising a switching unit that switches the sheet fed from the nip portion so as to be conveyed toward either the first conveying guide member or the second conveying guide member.

9. The transport guide member is The angle of inclination toward the outlet side is adjustable, 3. The heating and conveying device according to claim 1, wherein the angle is adjusted to be larger when a sheet having a basis weight equal to or greater than a predetermined value is conveyed than when a sheet having a basis weight less than the predetermined value is conveyed.

10. 3. The heating and conveying device according to claim 1, wherein the fixing device includes a heat equalizing member that contacts the planar heater and equalizes the heat generated in the planar heater.

11. 3. An image forming apparatus comprising the heating and conveying device according to claim 1.

Images