JP6268073B2 - Fixing unit and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing unit and an image forming apparatus, and is suitable for application to, for example, an electrophotographic printer (hereinafter also referred to as a printer) and a fixing unit provided in the printer.

  In a conventional image forming apparatus, a swing lever is provided in a fixing device so as to be swingable around a fulcrum at one end, and a main shaft of a fixing roller is supported by the swing lever. In the image forming apparatus, a pressure roller and a heating roller are provided in the fixing device, and an endless belt is stretched between the heating roller and the fixing roller. Then, the image forming apparatus pushes down the swing lever in the fixing device and presses the fixing roller against the pressure roller via the endless belt when forming the print image, thereby endlessly transferring the medium having the toner image transferred to the surface. The toner image was fixed on the surface of the medium by heating and pressing while being conveyed through a belt and a pressure roller. In addition, when the print image is not formed, the image forming apparatus pushes up the swing lever in the fixing device and separates the fixing roller from the pressure roller, so that the fixing roller, the pressure roller, or the endless belt is formed. The distortion caused by pressing was prevented (for example, see Patent Document 1).

JP 2004-287131 A (pages 5 to 9, FIG. 2, FIG. 5)

  By the way, in the conventional image forming apparatus, for example, the fixing device is provided with a heating rotator and a pressure rotator, and has an elastic part in which a surface forms a bend that makes a pair substantially equal to the bend of the surface of the heating rotator. If a pressure pad is provided, a belt is passed between the pressure rotator and the pressure pad, and the elastic part of the pressure rotator and the pressure pad is pressed against the heating rotator via the belt, heating is performed. It is considered that the clamping range along the conveyance direction of the medium by the rotating body and the belt can be expanded. Even in the image forming apparatus having such a configuration, when the print image is not formed, the heating rotator is placed on the belt or the pressure rotator by separating the elastic portions of the pressure rotator and the pressure pad from the heating rotator. It is thought that distortion due to the pressing to the surface can be prevented. However, in the image forming apparatus having such a configuration, the pressure rotator and the elastic portion of the pressure pad are separated from the heating rotator while the temperature of the elastic portion of the pressure pad is relatively high as the toner image is heated. When naturally cooled, the elastic part of the pressure pad contracts and the bending may be deformed so as not to follow the bending of the heating rotator. In the image forming apparatus having such a configuration, when the pressure rotator and the elastic part of the pressure pad are pressed against the heating rotator via the belt again for forming a print image, the heating rotator is deformed by the deformation of the elastic part. When the pressing force at the pressing portion becomes uneven, and the toner image on the surface of the medium is heated and pressed, at least a part of the toner image has a misalignment of the fixing position, a fixing defect that easily peels off, and the like. There was a problem that the quality of the product deteriorated.

  The present invention has been made in consideration of the above points, and an object of the present invention is to propose a fixing unit and an image forming apparatus capable of preventing deterioration in quality of a printed image.

In order to solve this problem, in the present invention, a fixing unit that heats and fixes a developer image on the surface of a medium, a heating rotator for heating the medium, a belt for sandwiching the medium together with the heating rotator, and a belt A pressure rotating body that pushes the belt in the direction of the heating rotator, an elastic part that has a bend that is paired with the bending of the heating rotator, a pressure pad that pushes the belt in the direction of the heating rotator, and operation of the operation unit When the operation unit is moved to the rotary body separation operation position, the operation unit is held at the rotary body separation operation position , and the pressure rotation body is moved. holds the separated state from the heating rotating body, a pressure pad is provided with a holding portion for holding a position of contacting the belt and the heating rotating body, the movement unit, the unit is a predetermined period of time, when not in use The operation unit is in the rotary body separation operation position. When the jammed medium is removed from the unit by moving the pressure rotator away from the heating rotator, leaving the belt in contact with the heating rotator with the pressure pad. When the operating unit is operated to a rotating pad separation operation position different from the rotating body separation operation position, the pressure pad and the pressure rotation body are moved away from the heating rotation body to be separated.

Therefore, in the present invention, when the unit is not used for a predetermined period, even if the operation unit is operated with the temperature of the elastic part of the pressure pad being relatively high as the developer image is heated, In addition, the elastic part of the pressure pad is contracted by natural cooling and the bending does not follow the bending of the heating rotator while preventing the belt from being distorted by pressing the same part on the heating rotator. As a result, when the pressure rotator is moved again to heat the developer image so as to push the belt in the direction of the heating rotator, Forming a print image by accurately fixing the developer image on the surface of the medium, almost certainly avoiding the non-uniform pressing force of the pressing portion against the heating rotator via the belt by the elastic portion. it is, Ja from the unit Even when the medium is removed, thereby operating portion is spaced a belt with pressure rotating body and the pressure pad from the heating rotating body by manipulating the jam medium easily removed.

According to the present invention, the fixing unit that heats and fixes the developer image on the surface of the medium, the heating rotator for heating the medium, the belt for sandwiching the medium together with the heating rotator, and the belt of the heating rotator. It has a pressure rotating body that pushes in the direction and an elastic part that has a bend that is paired with the bending of the heating rotating body, and pressurizes according to the operation of the pressure pad that pushes the belt in the direction of the heating rotating body and the operation part When the moving unit that moves the rotating body and the pressure pad and the operation unit are operated to the rotating body separating operation position, the operating unit is held at the rotating body separating operation position, and the pressurizing rotating body is removed from the heating rotating body . holds the separated state, the pressure pad is provided with a holding portion for holding a position of contacting the belt and the heating rotating body, the movement unit, the unit is a predetermined time period, the rotating body operation unit when not in use When operated to the remote operation position, While the belt is in contact with the heating rotator, the pressurizing rotator is moved away from the heating rotator to separate it, and when the jammed medium is removed from this unit, the operating unit is operated to separate the rotator. When operated in different rotational body pad separation operation position of the position, pressure pad and the separated state and to isosamples the rotating pressing body is moved in a direction away from the heating rotating body, the unit is a predetermined time period, Even when the operating portion is operated with the temperature of the elastic portion of the pressure pad being relatively high as the developer image is heated when the developer image is heated, the pressure rotator and the belt are not While preventing distortion due to pressing, it is possible to almost certainly prevent the elastic part of the pressure pad from being deformed so that the bending does not follow the bending of the heating rotating body due to contraction due to natural cooling. And, as a result, again When the pressure rotator is moved to heat the image agent image so as to push the belt in the direction of the heating rotator, the pressing force of the pressing portion to the heating rotator via the belt by the elastic part of the pressure pad Can be almost surely avoided, and the developer image can be accurately fixed on the surface of the medium to form a printed image, and when the jammed medium is removed from the unit, The fixing unit and the image which can operate the operation unit to separate the belt together with the pressure rotator and the pressure pad from the heating rotator and easily remove the jammed medium , thus preventing the deterioration of the quality of the printed image. A forming apparatus can be realized.

1 is a schematic side view showing an internal configuration of a printer according to the present invention. FIG. 3 is a schematic perspective view illustrating an external configuration of a fixing unit. FIG. 3 is a schematic perspective view showing an internal configuration (1) of the fixing unit. FIG. 6 is a schematic perspective view showing an internal configuration (2) of the fixing unit. FIG. 10 is a schematic side view showing an internal configuration (3) of the fixing unit. FIG. 6 is a schematic cross-sectional view showing an internal configuration (4) of the fixing unit. It is the rough-line front view and rough-line sectional drawing which show the structure of a heating roller. It is the rough-line front view and rough-line sectional drawing which show the structure of a pressure roller. It is the rough-line front view and rough-line sectional drawing which show the structure of a pressure pad. It is the rough-line front view and rough-line sectional drawing which show the structure of a pressure belt. It is an approximate line sectional view used for explanation of press (1) of a pressure roller and a pressure pad to a heating roller. It is an approximate line fragmentary sectional view used for description of pressing of a pressure roller and a pressure pad to a heating roller (2). It is an approximate line sectional view used for explanation of separation (1) of a pressure roller and a pressure pad from a heating roller. It is an approximate line fragmentary sectional view used for description of separation (2) of a pressure roller and a pressure pad from a heating roller. It is an approximate line sectional view used for explanation of separation (1) of only a pressure roller from a heating roller. It is an approximate line fragmentary sectional view used for description of separation (2) of only a pressure roller from a heating roller. FIG. 10 is a schematic cross-sectional view showing an internal configuration of another fixing unit. It is a rough-line perspective view which shows the structure of a lock piece. FIG. 10 is a schematic perspective view for explaining the separation of a pressure roller and a pressure pad from a heating roller using a lock piece by another fixing unit.

The best mode for carrying out the invention (hereinafter, also referred to as an embodiment) will be described below with reference to the drawings. The description will be given in the following order.
(1) Embodiment (2) Other embodiments

(1) Embodiment (1-1) Internal Configuration of Printer In FIG. 1, reference numeral 1 denotes a direct transfer type monochrome printer as a whole according to the present invention. The printer 1 includes a substantially square box type printer housing 2 whose right end surface in the drawing is the front surface 2A, for example. Incidentally, in the following description, when the printer 1 is viewed facing the front surface 2A of the printer housing 2, the direction above the printer 1 indicated by the arrow a1 in the figure is also referred to as the printer upward direction. The direction opposite to the upward direction is also referred to as the printer downward direction, and when there is no need to distinguish between them, they are collectively referred to as the printer vertical direction. Further, in the following description, the direction in front of the printer 1 indicated by the arrow b1 in the drawing when the printer 1 is viewed facing the front surface 2A of the printer housing 2 is also referred to as the front direction of the printer. The direction opposite to the forward direction is also referred to as the rear direction of the printer, and when it is not necessary to distinguish between them, they are collectively referred to as the front and rear direction of the printer. Further, in the following description, the left direction of the printer 1 indicated by the arrow c1 in the figure when the printer 1 is viewed facing the front surface 2A of the printer housing 2 is also referred to as the printer left direction. The direction opposite to the left direction is also referred to as the right direction of the printer, and when there is no need to distinguish between them, they are collectively referred to as the left and right direction of the printer.

  The printer 1 forms the print image on the surface of a medium such as recording paper or film (hereinafter also referred to as a print medium) 5 used for forming the print image. At the rear end, a medium delivery unit 2BX that delivers the print medium 5 on which the print image is formed, and a medium discharge port 2BY that ejects the print medium 5 from the printer housing 2 to the medium delivery unit 2BX are formed. ing. In the printer housing 2, an image forming unit 6 for forming a print image on the surface of the print medium 5 is disposed at the center, and a plurality of print media 5 can be loaded at the lower end. A cassette 7 and a feed roller 8 and a separation roller 9 for feeding the print media 5 from the medium cassette 7 one by one are arranged. The image forming unit 6 includes an image forming unit 10, a transfer roller 11, and a fixing unit 12. For example, the image forming unit 10 is provided so as to be rotatable in one rotation direction indicated by an arrow d1 in the drawing, and is exposed to an LED (Light Emitting Diode) head 16 on the surface of the photosensitive drum 15 charged to a predetermined negative potential. Then, an electrostatic latent image is formed, and the electrostatic latent image is developed with black toner as a developer charged to a predetermined negative potential to form a toner image as a developer image. The transfer roller 11 is provided so as to be able to rotate in the other rotation direction opposite to the one rotation direction with the surface pressed against the surface of the photosensitive drum 15 with a predetermined pressing force. In this state, the toner image on the photosensitive drum 15 is transferred to the printing medium 5. The fixing unit 12 fixes the toner image on the surface of the print medium 5 by heating and pressing. Incidentally, in the printer casing 2, a medium supply transport unit 17 that forms a medium supply transport path for transporting the print medium 5 fed from the medium cassette 7 to the image forming unit 6 is disposed at the front lower end. Has been. The medium supply transport unit 17 is provided with a pair of registration rollers 18 in the middle of the medium supply transport path to correct the transport posture with one end of the print medium 5 facing the transport direction parallel to the left-right direction of the printer. ing. In the printer casing 2, a medium discharge transport unit 19 that forms a medium discharge transport path for transporting the print medium 5 fed from the fixing unit 12 to the medium discharge port 2BY is disposed at the rear upper end. ing.

  In the printer housing 2, for example, a printer control unit (not shown) such as a microprocessor that performs overall control of the entire printer 1 is provided. When forming a print image, the printer control unit drives and controls each unit in the printer casing 2 to feed out the print media 5 from the medium cassette 7 one by one and through the medium supply conveyance path, the image formation unit 6. Transport to. At this time, the printer control unit controls the LED head 16 according to the black color component of the monochrome image to be printed based on the image data, for example, so that the electrostatic latent image is formed on the surface of the photosensitive drum 15 in the image forming unit 10. An image is formed, and the electrostatic latent image is developed with toner to form a black toner image. The printer control unit transfers the toner image from the surface of the photosensitive drum 15 to the surface of the printing medium 5 while conveying the printing medium 5 by the photosensitive drum 15 and the transfer roller 11, and then the printing medium 5 by the fixing unit 12. A toner image is fixed on the surface of the sheet to form a monochrome print image, and the print medium 5 is conveyed to the medium discharge port 2BY via the medium discharge conveyance path and discharged to the medium delivery unit 2BX.

(1-2) Configuration of Fixing Unit Next, the configuration of the fixing unit 12 will be specifically described. As shown in FIG. 2, the fixing unit 12 has a substantially box-shaped unit housing 20 that is long in the left-right direction of the printer. The unit housing 20 is formed with a medium intake port 20AX on the front surface 20A for taking in the print medium 5 on which the toner image is transferred by the photosensitive drum 15 and the transfer roller 11, and on the rear surface 20B. A medium discharge port (not shown) for discharging the print medium 5 on which the print image is formed to the medium discharge conveyance path is formed. The unit housing 20 has, for example, a lever operation opening 20CX that is long in the front-rear direction of the printer at a predetermined position near the right end of the upper surface 20C, and a distal end of an operation lever 21 described later is connected to the lever operation opening 20CX. Projecting upward. As shown in FIGS. 3 to 6, the unit housing 20 houses a substantially U-shaped unit frame 28 comprising a left side plate 25, a right side plate 26, and a bottom plate 27 connecting them. Yes. In the unit casing 20, a heating unit 30 for heating the printing medium 5 and a pressing unit 31 for pressing the printing medium 5 together with the heating unit 30 are vertically moved via the unit frame 28. It is provided adjacent to. The heating unit 30 mainly includes a heating roller 35, a pair of heaters 36 and 37, and a pair of left heater support unit 38 and right heater support unit 39. The pressure unit 31 mainly includes a pressure roller 40, a pair of left roller support unit 41 and right roller support unit 42, a pressure pad 43, a pair of left pad support unit 44 and a right pad support unit 45, And a displacement restricting portion 46 and an endless belt for pressurization (hereinafter also referred to as a pressurization belt) 47.

  As shown in FIGS. 7A to 7C, in the heating unit 30, the heating roller 35 is arranged at the center of the outer peripheral surface of the core metal 35 </ b> A that is a hollow pipe that is open at both ends of a metal such as iron or aluminum (that is, On the outer peripheral surface, the entire circumference of the heating roller 35 extends along the central axis AX1 except for one end and the other end), PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer) or PTFE (polytetrafluoro). A resin layer 35B such as ethylene (tetrafluoride) is provided and formed. Incidentally, in the fixing unit 12 that wants to shorten the startup time as much as possible, or in the fixing unit 12 incorporated in the monochrome printer 1 with high mobility, the heating roller 35 has a relatively high thermal conductivity, and the heater It is preferable to provide an aluminum core bar 35A that can shorten the time from the start of heating by 36 and 37 until reaching a predetermined temperature for toner image fixing as much as possible. In the present embodiment, the fixing unit 12 has a thickness of about 30 [μm] at the central portion of the outer peripheral surface of the core metal 35A of an A5056 aluminum alloy having a thickness of about 1.5 [mm]. The PFA is provided as the resin layer 35B and has a radius R1 of about 14 [mm] (that is, a distance from the center axis AX1 of the heating roller 35 to the surface of the heating roller 35 which is also the surface of the resin layer 35B). The heated roller 35 is provided. In the unit frame 28 (FIGS. 3 to 6), a left roller support hole and a right roller support hole are formed at opposite positions of the center of the inner surface of each of the left plate 25 and the right plate 26. A first left bearing 52 and a first right bearing 53 are attached to the first and right roller support holes through a cylindrical left sleeve 50 and a right sleeve 51. The unit frame 28 is fixed by inserting one end portion of the heating roller 35 into the first left bearing 52 and is fixed by inserting the other end portion of the heating roller 35 into the first right bearing 53. As a result, the unit frame 28 supports the heating roller 35 by the left side plate 25 and the right side plate 26 so as to be rotatable in one rotation direction around the central axis AX1 parallel to the horizontal direction of the printer. By the way, the unit frame 28 is provided with a drive gear 55 rotatably at a predetermined position on the outer surface of the right side plate 26 via a gear shaft parallel to the left and right direction of the pudding. Is connected to an output gear (not shown) fixed to an output shaft of a fixing unit driving motor (not shown) via one or a plurality of intermediate gears (not shown). The heating roller 35 has, for example, the other end portion protruding from the first right bearing 53 to the outer surface side of the right side plate 26, and a roller gear (not shown) is attached to the protruding portion. The unit frame 28 meshes the drive gear 55 with the roller gear in a state where the heating roller 35 is rotatably supported via the left side plate 25 and the right side plate 26.

  The pair of heaters 36 and 37 are both halogen lamps, for example, and are formed to have a predetermined length that is longer than that of the heating roller 35. The left heater support portion 38 and the right heater support portion 39 are each formed, for example, in a substantially L-shaped plate shape, provided with a mounting portion bent at a substantially right angle at one end of the shoulder portion, and a pair of notches in the arm portion. Shaped terminal engaging portions are formed side by side. Further, the unit frame 28 is suspended from the rear upper end portion of the left side plate 25 so that the left support portion mounting plate 25A protrudes to the outer surface side, and the right support portion mounting plate 26A is provided at the rear upper end portion of the right side plate 26. Is suspended so as to protrude to the outer surface side. In the unit frame 28, a pair of heaters 36 and 37 are inserted into the heating roller 35, and the pair of heaters 36 and 37 are connected to the pair of terminal engaging portions of the arm portion of the left heater support portion 38 on the outer surface side of the left side plate 25. 37, the attachment portion of the left heater support portion 38 is fixed to the left support portion attachment plate 25 </ b> A of the left side plate 25 in a state in which the terminals on one end side of each are engaged. Further, the unit frame 28 is engaged with the pair of terminal engaging portions of the arm portion of the right heater support portion 39 on the outer surface side of the right side plate 26 so that the terminals on the other ends of the pair of heaters 36 and 37 are inserted. In this state, the attachment portion of the right heater support portion 39 is fixed to the right support portion attachment plate 26A of the right side plate 26. As a result, the unit frame 28 moves the pair of heaters 36 and 37 from the left side plate 25 and the right side plate 26 via the left heater support portion 38 and the right heater support portion 39 without contacting the inner surface of the heating roller 35. Parallel and support side by side. In addition, each of the pair of heaters 36 and 37 has a terminal on one end side and a terminal on the other end side electrically connected to a heater power source in the printer casing 2. Thus, the heating unit 30 can rotate the heating roller 35 in one rotation direction according to the operation of the fixing unit driving motor, and in that state, the pair of heaters 36 and 37 can generate heat according to the power supply from the heater power source. The heating roller 35 can be heated from the inside. Incidentally, the left sleeve 50 and the right sleeve 51 described above are formed of, for example, conductive heat-resistant resin, and when the heating roller 35 is heated by the pair of heaters 36 and 37, the heat of the core metal 35A is changed to the first left bearing. 52 and the first right bearing 53 function as a heat insulator that suppresses heat dissipation. Thereby, the heating unit 30 heats the heating roller 35 as efficiently as possible when the pair of heaters 36 and 37 generate heat.

  On the other hand, as shown in FIGS. 8A to 8C, in the pressure unit 31, the pressure roller 40 is provided on one end surface and the other end surface of a cored bar 40A that is a hollow pipe that is closed at both ends of a metal such as iron. Each of the roller shafts 40B is suspended, and the entire outer peripheral surface of the cored bar 40A is improved in peelability with respect to the elastic layer 40C having heat resistance such as silicon rubber and the pressure belt 47, and has a frictional force. A coating layer 40D, which is a film-like carbon for reduction, is sequentially laminated. Further, the left roller support portion 41 and the right roller support portion 42 (FIGS. 3 to 6) are, for example, substantially F-shaped plates on the upper edges of the left support portion main body 41A and the right support portion main body 42A that are substantially elliptical plates, respectively. The left cam engagement portion 41B and the right cam engagement portion 42B are projected. The left roller support portion 41 and the right roller support portion 42 are closer to the center on one surface of the left support portion main body 41A and the right support portion main body 42A (that is, closer to the left cam engagement portion 41B and the right cam engagement portion 42B). In addition, a circular roller insertion hole portion having a diameter larger than the outer diameter of the heating roller 35 is formed, and a pad insertion hole portion and a roller support hole portion are connected to the roller insertion hole portion near the lower center. And it is drilled side by side. In addition, the left roller support portion 41 and the right roller support portion 42 are, for example, at the center of the rear end that is near the boundary between the roller insertion hole portion and the roller support hole portion on one surface of the left support portion main body 41A and the right support portion main body 42A. A shaft insertion hole is formed. Further, the unit frame 28 has a left rotation shaft 56 and a right rotation shaft 57 implanted near the lower ends of the rear end portions of the inner surfaces of the left side plate 25 and the right side plate 26. The unit frame 28 is placed in the left side of the shaft insertion hole of the left roller support 41 with one end of the heating roller 35 inserted in the roller insertion hole of the left roller support 41 on the inner surface side of the left side plate 25. A rotating shaft 56 is inserted. The unit frame 28 is inserted into the shaft insertion hole portion of the right roller support portion 42 in a state where the other end portion of the heating roller 35 is inserted into the roller insertion hole portion of the right roller support portion 42 on the inner surface side of the right side plate 26. A right rotation shaft 57 is inserted. As a result, the unit frame 28 moves the left roller support portion 41 and the right roller support portion 42 around the left rotation shaft 56 and the right rotation shaft 57 parallel to the horizontal direction of the printer. It is supported so as to be rotatable in the rotational direction and other rotational directions. In addition, the pressure roller 40 has a roller shaft 40 </ b> B on one end surface side attached to the roller support hole portion of the left roller support portion 41 via the second left bearing 58 and the roller support hole portion of the right roller support portion 42. 2 A roller shaft 40B on the other end surface side is attached via a right bearing 59. As a result, the unit frame 28 moves the pressure roller 40 through the left roller support portion 41 and the right roller support portion 42 by the left side plate 25 and the right side plate 26 around the pair of roller shafts 40B parallel to the left and right direction of the printer. It is supported so as to be able to rotate in other rotational directions.

  Further, as shown in FIGS. 9A to 9C, the pressure pad 43 is made of a metal such as iron or aluminum and has a substantially strip-shaped elastic layer arrangement portion 43AX and a substantially strip-shaped displacement regulating engagement portion 43AY. Are connected to each other via a substantially strip-shaped connecting portion 43AZ, and has a pad main body 43A that is a rod formed in a substantially letter E shape. The pressure pad 43 is integrally provided with one end-side locking projections 43B and other end-side locking projections 43C on the one end and the other end of the pad main body 43A, and the outer surface of the elastic layer arrangement portion 43AX. On one surface of the pad main body 43A (hereinafter also referred to as one surface of the pad), the heat-resistant elastic layer 43D such as silicon rubber and the peelability with respect to the pressure belt 47 are improved and the frictional force is reduced. A coating layer 43E, which is a film-like carbon, is laminated in order. The pressure pad 43 is formed so that the elastic layer 43 </ b> D has a bend that is paired with the bend of the heating roller 35. In other words, the pressure pad 43 is formed such that the surface of the elastic layer 43 </ b> D has an arc concave shape with a curvature that is substantially equal to the curvature of the surface of the heating roller 35. In the present embodiment, the surface of the elastic layer 43D of the pressure pad 43 has a radius of curvature R2 of about 14.1 [mm] which is substantially equal to the radius R1 selected to be about 14 [mm] of the heating roller 35. It is formed in an arc concave shape. The pressure pad 43 (FIGS. 3 to 6) is inserted into the pad insertion hole portion of the left roller support portion 41 and the pad insertion hole portion of the right roller support portion 42 in order with the surface of the elastic layer 43D facing upward. Has been. The pair of left pad support portion 44 and right pad support portion 45 are each formed in a substantially U-shaped plate shape, and one end side locking projection 43B and the other end side locking projection 43C of the pressure pad 43 are formed on one end of one surface. 44A (only one is shown and the other is not shown) corresponding to the above, and the shaft insertion hole 44B (only one is shown and the other is not shown) on the other end of the one surface. ) Is drilled. The left pad support 44 has a left rotation shaft 56 inserted into the shaft insertion hole 44B between the left side plate 25 and the left roller support 41, and an arcuate central portion is connected to one end of the pressure roller 40. After being detoured so as to pass through the lower side of the portion, the one end side locking projection 43B of the pressure pad 43 is inserted into the locking hole portion 44A and locked. Further, the right pad support portion 45 has a right rotation shaft 57 inserted into the shaft insertion hole between the right side plate 26 and the right roller support portion 42, and an arcuate central portion at the other end of the pressure roller 40. The other end side locking projection 43C of the pressure pad 43 is inserted and locked in the locking hole portion. As a result, the unit frame 28 moves the left pad support 44 and the right pad support 45 with the left plate 25 and the right plate 26 around the left rotation shaft 56 and the right rotation shaft 57 parallel to the horizontal direction of the printer. The pressure pad 43 is supported by the pair of the left pad support portion 44 and the right pad support portion 45 in the vicinity of the front side of the pressure roller 40 and is supported by the left rotation shaft 56. And it supports so that it can displace to one rotation direction and another rotation direction centering on the right rotation axis | shaft 57. FIG.

  The displacement restricting portion 46 is formed, for example, in a substantially channel shape (that is, a substantially U-shaped cross section) that is long in the left-right direction of the printer with a predetermined metal, and has one end portion and the other end portion in a posture with its bottom face facing upward. Is fixed to a position opposite to the lower end portions of the inner surfaces of the left roller support portion 41 and the right roller support portion 42. The displacement restricting portion 46 is a pair of substantially L-shaped left restrictors at a predetermined position on the left side of the upper end and a predetermined position on the right side of the upper end of one plate portion (hereinafter also referred to as a restricting plate portion) 61A located on the front side. The claw portion 46B and the right restricting claw portion 46C are provided so as to protrude from each other. Here, in the displacement restricting portion 46, the distance between the upper end of the restricting plate portion 61A and the tip ends of the left restricting claw portion 46B and the right restricting claw portion 46C is the thickness of the displacement restricting engagement portion 43AY of the pressure pad 43. A wider predetermined interval is selected. Therefore, in the displacement restricting portion 46, one end portion of the displacement restricting engagement portion 43AY of the pressure pad 43 is inserted between the portion on the left side of the upper end of the restricting plate portion 61A and the tip of the left restricting claw portion 46B. The other end portion of the displacement restricting engagement portion 43AY is inserted between the portion of the plate portion 61A on the right side of the upper end and the tip portion of the right restricting claw portion 46C. As a result, the displacement restricting portion 46 places the pressure pad 43 on the other surface of the pad main body 43A, which is the outer surface of the displacement restricting engaging portion 43AY, on the upper end of the restricting plate portion 61A (hereinafter also referred to as the other surface of the pad). One end portion and the other end portion of the inner surface of the displacement restricting engagement portion 43AY (hereinafter referred to as one end portion of the restricting surface) from the contact position to the tip portion of the pair of left restricting claw portions 46B and the tip portion of the right restricting claw portion 46C. And also called the other end portion of the regulating surface). The pressurizing unit 31 includes a plurality of compression coil springs 60 having a similar configuration and having a predetermined elastic force. The plurality of compression coil springs 60 are arranged at predetermined intervals along the left-right direction of the printer between the bottom surface of the displacement restricting portion 46 and the other surface of the pressure pad 43, and one end of each of the compression coil springs 60 is disposed on the bottom surface. While being locked, each other end is locked to the other surface of the pad. Thereby, the pressurizing unit 31 is urged by the plurality of compression coil springs 60 so as to push up the pressurizing pad 43. In the following description, the plurality of compression coil springs 60 that bias the pressure pad 43 are also referred to as pad biasing springs 60, respectively.

  By the way, the left roller support part 41 and the right roller support part 42 are belts whose surfaces are formed in an arcuate or arcuate shape at the opposing positions of the inner rear lower end of the left support part main body 41A and the right support part main body 42A. A guide 61 (only one is shown but the other is not shown) is fixed with the surface facing obliquely downward, and the surface is also formed in an arcuate shape or arc shape at a position opposite to the front end of the inner surface. A belt guide 62 (only one is shown and the other is not shown) is fixed with its surface facing forward. Further, as shown in FIGS. 10A to 10C, the pressure belt 47 has a release layer 47B laminated on the entire outer peripheral surface of a resin belt body 47A such as a polyimide resin. It is formed into an endless film having high strength and relatively high heat resistance. The pressure belt 47 (FIGS. 3 to 6) is stretched between the left roller support portion 41 and the right roller support portion 42 on the pressure roller 40, the elastic layer 43D of the pressure pad 43, and the belt guides 61 and 62. It is built. The pressurizing unit 31 also includes a pair of left compression coil spring 63 and right compression coil spring 64 having the same configuration and having a predetermined elastic force larger than the elastic force of the plurality of pad urging springs 60, for example. Further, the unit frame 28 is suspended so that the spring locking plates 25B and 26B protrude inwardly at positions opposite to the rear upper ends of the left side plate 25 and the right side plate 26, and the rear side of these spring locking plates 25B and 26B. Spring locking protrusions 25BX and 26BX are provided at predetermined positions on the surface facing the surface. The left compression coil spring 63 has one end inserted into the spring locking projection 25BX of the left side plate 25 and locked to the spring locking plate 25B, and the other end connected to the left cam support of the left roller support 41. Of the pair of protrusions protruding to the front side of the joint portion 41B, a spring locking protrusion 41BX, which is a lower protrusion, is inserted inside and locked to the left cam engagement portion 41B. The right compression coil spring 64 has one end inserted into the spring locking projection 26BX of the right side plate 26 and locked to the spring locking plate 26B, and the other end connected to the right cam support of the right roller support portion 42. Of the pair of protrusions protruding to the front side of the joint portion 42B, a spring locking protrusion 42BX, which is a lower protrusion, is inserted inside and locked to the right cam engaging portion 42B. As a result, the pressurizing unit 31 urges the left roller support unit 41 and the right roller support unit 42 to rotate in the other rotation directions by the left compression coil spring 63 and the right compression coil spring 64, and the pressure is increased accordingly. The pressure roller 40 is also urged to be pushed up. Incidentally, in the following description, the left compression coil spring 63 for biasing the pressure roller 40 so as to push it up is also referred to as a left roller bias spring 63, and the right compression coil spring 64 is referred to as a right roller bias spring 64. Call.

  In addition to such a configuration, in the case of this embodiment, the fixing unit 12 has a pair of left cam portion 70 and right cam portion 71 and a lever shaft 72 together with the operation lever 21 described above. Further, a separation control unit 73 is provided for moving the pressure roller 40 so as to push the pressure belt 47 toward the heating roller 35 and moving the pressure roller 47 away from (i.e., separate from) the heating roller 35. In the separation control unit 73, the operation lever 21 is formed in a substantially square block shape, the length of the lever base 21A is selected to be longer than the length of the lever tip 21B, and the end of the lever base 21A is D. A character-shaped shaft insertion hole is formed. Incidentally, in the following description, the surface of the lever base portion 21A of the operating lever 21 on the side where the bent portion with the lever tip portion 21B has a mountain shape is also referred to as one surface of the lever root portion, and is bent with the lever tip portion 21B. The surface on the side where the portion is valley-shaped is also referred to as the lever root other surface. The left cam portion 70 and the right cam portion 71 are each formed in a substantially obtuse triangular block shape, and a D-shaped left shaft insertion hole portion and right shaft insertion hole portion are formed at the apex portion of the obtuse angle. Incidentally, in the following description, one of the slopes of the left cam portion 70 and the right cam portion 71 that contact each other at the apex portion of the obtuse angle and the other slope is also referred to as one-side slope, and the other slope is referred to as the other-side slope. A substantially flat surface from one remaining vertex portion to the other vertex portion is also referred to as a cam bottom surface. Further, the left cam portion 70 and the right cam portion 71 have one end pressing portion 70A having an end surface formed in an arc shape or a bow shape at one of the other apex portions excluding the apex portion of the obtuse angle, and The right end side pressing portion 71A protrudes, and the other end portion has a flat end surface at the left other end side pressing portion 70B and the right other end side pressing portion 71B. It protrudes in contact with the side slope at an obtuse angle. Further, the left cam portion 70 and the right cam portion 71 are the length from the left shaft insertion hole to the end surface of the left one end side pressing portion 70A, and the length from the right shaft insertion hole to the end surface of the right one end side pressing portion 71A. (Hereinafter, these are also referred to as cam one end side lengths) are selected to have the same predetermined length, the length from the left shaft insertion hole portion to the end surface of the left other end pressing portion 70B, and the right shaft insertion hole. The length from the first end to the end face of the right other end pressing portion 71B (hereinafter also referred to as the cam other end side length) is selected to be the same predetermined length shorter than the cam one end side length. The lever shaft 72 has, for example, a D-cut surface corresponding to the shape of the left shaft insertion hole of the left cam 70 at the left end, and the shape of the shaft insertion hole of the operation lever 21 and the right at the right end. A D-cut surface corresponding to the shape of the right shaft insertion hole of the cam portion 71 is formed. The lever shaft 72 is inserted at the left end portion into the left shaft insertion hole portion of the left cam portion 70, and the right end portion is inserted into the shaft insertion hole portion of the operation lever 21 and the right shaft insertion hole portion of the right cam portion 71 in order. Has been. As a result, the separation control unit 73 fixes the operation lever 21 to the lever shaft 72, and the left cam portion 70 and the right cam portion 71 respectively change the left one end pressing portion 70A and the right one end pressing portion 71A to the lever tip portion 21B. And the left other end side pressing part 70B and the right other end side pressing part 71B are fixed by projecting to the side of the lever base part facing one surface. Further, the unit frame 28 has a left shaft insertion hole portion 25C and a right shaft insertion hole portion 26C formed at opposing positions of the rear upper corners on the inner surfaces of the left side plate 25 and the right side plate 26, respectively. The left end portion of the lever shaft 72 is inserted, and the right end portion of the lever shaft 72 is inserted into the right shaft insertion hole portion 26C. As a result, the unit frame 28 has its lever shaft in a state in which the operation lever 21, the left cam portion 70, and the right cam portion 71 are integrated with the lever shaft 72 parallel to the left-right direction of the printer by the left side plate 25 and the right side plate 26. It is supported so as to be rotatable in one rotation direction and the other rotation direction around 72. Further, the left roller support part 41 and the right roller support part 42 are respectively provided with a left cam pressing member facing the left cam part 70 and the right cam part 71 at the rear edges of the left cam engagement part 41B and the right cam engagement part 42B. The plate 41BY and the right cam pressing plate 42BY are provided so as to protrude outward. As a result, the separation control unit 73 moves the left cam unit 70 and the right cam to the left cam pressing plate 41BY and the right cam pressing plate 42BY of the left roller support unit 41 and the right roller support unit 42 according to the rotation operation of the operation lever 21. The left one end pressing portion 70A and the right one end pressing portion 71A of the portion 71 are pressed, and the left other end pressing portion 70B and the right other end pressing portion 71B are pressed, and the left roller support portion 41 and the right roller support portion are pressed. 42 can be rotated in one rotation direction.

  Here, in the fixing unit 12, the natural lengths and spring constants of the left roller urging spring 63, the right roller urging spring 64, and the plurality of pad urging springs 60 are appropriately selected, and the shapes of the above-described components, The size, dimensions, support position, etc. are also appropriately selected. Therefore, as shown in FIGS. 11 and 12, the fixing unit 12 performs an operation of setting the operation lever 21 to the operation reference posture in which the lever base portion 21 </ b> A is slightly inclined to the front side when the operation lever 21 is not rotated at all. At the reference position, the cam bottom surfaces of the left cam portion 70 and the right cam portion 71 are made substantially vertical accordingly. When the operation lever 21 is positioned at the operation reference position, the fixing unit 12 causes the left roller support portion 41 and the right roller support portion 42 to move to the left by the bias of the left roller bias spring 63 and the right roller bias spring 64. The surface of the pressure roller 40 and the surface of the elastic layer 43 </ b> D of the pressure pad 43 are interposed via the pressure belt 47 so as to rotate in the other rotation direction around the rotation shaft 56 and the right rotation shaft 57. It can be pressed against the surface of the heating roller 35. At this time, the fixing unit 12 crushes the pressing portion of the elastic layer 40C of the pressure roller 40 against the heating roller 35 to some extent, and the surface of the pressure roller 40 is pressed against the pressure belt 47 with a desired first pressing force. Is pressed against the surface of the heating roller 35. When the fixing unit 12 presses the surface of the elastic layer 43D of the pressure pad 43 near the front side of the pressure roller 40 against the surface of the heating roller 35 via the pressure belt 47, the pressure pad 43 is correspondingly pressed. However, the plurality of pad urging springs 60 are pressed and contracted by the other surface of the pad, and the other surface of the pad is displaced in one rotation direction so as to approach the upper end of the restricting plate portion 61A of the displacement restricting portion 46. However, the fixing unit 12 causes the surface of the elastic layer 43D of the pressure pad 43 to be biased by the first pressing force by the plurality of pad biasing springs 60 contracted by the displacement of the pressure pad 43 in one rotation direction. Although it is slightly smaller, it can be pressed against the surface of the heating roller 35 via the pressure belt 47 with a desired second pressing force. In this way, the fixing unit 12 conveys the print medium 5 so as to be sandwiched between the portion where the pressure belt 47 is pressed by the pressure roller 40 on the surface of the heating roller 35 and the portion where the pressure belt 47 is pressed. A first sandwiching part NP1 for heating and pressurizing is formed. Further, the fixing unit 12 heats and transfers the print medium 5 while sandwiching the printing medium 5 between the portion where the pressure belt 47 is pressed by the pressure pad 43 on the surface of the heating roller 35 and the pressing portion of the pressure belt 47. A second sandwiching part NP2 for pressurization is formed. Incidentally, in the following description, a portion of the surface of the heating roller 35 where the pressure belt 47 is pressed by the pressure roller 40 (that is, a portion that forms the first sandwiching portion NP1 together with the pressure belt 47) is the roller side. Also referred to as a first pressing portion, a portion where the pressure belt 47 is pressed by the elastic layer 43D of the pressure pad 43 (that is, a portion that forms the second sandwiching portion NP2 together with the pressure belt 47) is the roller side second pressing. Also called a site. Further, in the following description, a portion of the surface of the pressure belt 47 that is pressed against the first pressing portion on the roller side of the heating roller 35 by the pressure roller 40 (that is, the first sandwiching portion NP1 is formed together with the heating roller 35). Part) is also referred to as a belt-side first pressing part, and the part pressed by the elastic layer 43D of the pressure pad 43 against the roller-side second pressing part of the heating roller 35 (that is, the second sandwiching part NP2 together with the heating roller 35) The part to be formed) is also called a belt side second pressing part.

By the way, when the operation lever 21 is positioned at the operation reference position, the fixing unit 12 causes the left roller support portion 41 and the right roller support portion 42 to be moved by the bias of the left roller bias spring 63 and the right roller bias spring 64, for example. Up to the roller pad pressing position that makes the left cam engagement portion 41B and the right cam engagement portion 42B substantially vertical without bringing the left cam portion 70 and the right cam portion 71 into contact with the left cam pressing plate 41BY and the right cam pressing plate 42BY. In the rotated state, the surface of the pressure roller 40 is pressed against the surface of the heating roller 35 via the pressure belt 47 with the first pressing force, and the surface of the elastic layer 43D of the pressure pad 43 is pressed with the second pressing force. It can be pressed against the surface of the heating roller 35 via the pressure belt 47. That is, the fixing unit 12 presses the surface of the pressure roller 40 with the first pressing force without being influenced by the left cam portion 70 and the right cam portion 71 whenever the position of the operation lever 21 is the operation reference position. The first sandwiching portion NP1 is formed by pressing against the surface of the heating roller 35 via the belt 47, and the entire surface of the elastic layer 43D of the pressure pad 43 is passed through the pressure belt 47 with a substantially uniform second pressing force. The second sandwiching portion NP2 can be formed by pressing against the surface of the heating roller 35. Then, when the fixing unit 12 forms the first sandwiching part NP1 and the second sandwiching part NP2, the fixing unit 12 can fix the toner image on the surface of the print medium 5 and form a print image. In other words, the fixing unit 12 generates heat in response to power supplied from the heater power source while rotating the heating roller 35 in one rotation direction in accordance with the operation of the fixing unit drive motor during the formation of the print image. The heating roller 35 is heated from the inside. Further, the fixing unit 12 rotates the pressure roller 40 together with the pressure belt 47 so as to rotate in the other rotation direction according to the rotation of the heating roller 35 in one rotation direction. In this manner, the fixing unit 12 heats the surface of the heating roller 35 to a desired temperature, and the heat is applied to the pressure belt 47 and the elastic layer 43D of the pressure roller 40 and the pressure pad 43 via the pressure belt 47. Then, the pressure belt 47 is also heated to a temperature substantially equal to the surface of the heating roller 35. In this state, when the printing medium 5 is transferred with the toner image transferred to the surface by the photosensitive drum 15 and the transfer roller 11 and conveyed, the upstream side of the printing medium 5 in the medium conveying direction MT1 is the printer casing. 2, and the downstream side is the back side of the printer housing 2, the print medium 5 is moved along the medium conveyance direction MT 1 and the second nipping portion NP 2 and the second nipping portion NP 2 of the heating roller 35 and the pressure belt 47. The toner image is fixed on the surface of the print medium 5 (that is, a print image is formed) by heating and pressurizing while being conveyed while being nipped in the nipping portion NP1 in order, and then to the medium discharge conveyance path. Can be handed over. The fixing unit 12 forms the first sandwiching part NP1 with the heating roller 35 and the pressure belt 47, and the second sandwiching part NP2 is upstream of the first sandwiching part NP1 in the medium transport direction MT1. They are formed close to each other. For this reason, the fixing unit 12 has, for example, a sandwiching portion as compared with a configuration in which the sandwiching portion is formed only from the heating roller and the pressure roller by pressing the pressure roller directly against the heating roller. The amount of heat applied to the print medium 5 for fixing the toner image can be increased by expanding the range of the image forming direction in the medium conveying direction MT1. As a result, the fixing unit 12 is used when the print medium 5 is conveyed at a relatively high speed as compared with a configuration in which the sandwiching portion is formed only from the heating roller and the pressure roller, even when the temperature is lowered to some extent, it is possible to accurately fix the toner image image on the surface of the printing medium 5. Further, the fixing unit 12 presses the surface of the pressure roller 40 against the surface of the heating roller 35 with the first pressing force through the pressing belt 47, and the surface of the elastic layer 43D of the pressing pad 43 with the first pressing force. Since the printing medium 5 conveyed along the medium conveyance direction MT1 is pressed by the second sandwiching part NP2 in order to be pressed through the pressure belt 47 with a slightly smaller second pressing force, the first sandwiching part It is possible to pressurize with NP1 at a pressure larger than that of the second sandwiching portion NP2, and the toner image can be efficiently and effectively fixed on the surface of the print medium 5.

  Further, as shown in FIGS. 13 and 14, the fixing unit 12 is, for example, manually operated by the user to rotate the operation lever 21 from the operation reference position in one rotation direction (that is, the lever base portion 21 </ b> A further than the operation reference posture). In response to this, the left cam portion 70 and the right cam portion 71 are also rotated in one rotation direction around the lever shaft 72. Accordingly, the fixing unit 12 presses the left end pressing portion 70A and the right end pressing portion 71A against the left cam pressing plate 41BY and the right cam pressing plate 42BY, so that the left roller biasing spring 63 and the right roller biasing spring are pressed. The left roller support portion 41 and the right roller support portion 42 can be rotated in one rotation direction around the left rotation shaft 56 and the right rotation shaft 57 while pressing and contracting 64. For example, when the operation lever 21 is rotated to the roller pad separation operation position in one rotation direction in which the operation lever 21 is set to the roller pad separation operation posture with the front end surface of the lever tip portion 21B facing upward, the fixing unit 12 is rotated. In response to the rotation of the left roller support portion 41 and the right roller support portion 42 in one rotation direction, the pressure roller 40 is displaced in one rotation direction to separate the pressure roller 40 from the heating roller 35. That is, the fixing unit 12 separates the belt-side first pressing portion of the pressure belt 47 from the roller-side first pressing portion of the heating roller 35 together with the pressure roller 40. In the fixing unit 12, the displacement restricting portion 46 is also displaced in one rotation direction away from the heating roller 35 in accordance with the rotation in the one rotation direction of the left roller support portion 41 and the right roller support portion 42. The pad urging spring 60 is extended, and one end portion and the other end portion of the restricting surface of the displacement restricting engagement portion 43AY of the pressure pad 43 are pressed against the tip ends of the left restricting claw portion 46B and the right restricting claw portion 46C. However, since the fixing unit 12 restricts the displacement range of the pressure pad 43 by the displacement restricting portion 46, the heating roller is urged so as to push up the pressure pad 43 by the plurality of pad urging springs 60. 35, the elastic layer 43D of the pressure pad 43 is separated. That is, the fixing unit 12 can separate the belt side second pressing portion of the pressure belt 47 from the roller side second pressing portion of the heating roller 35 together with the pressure pad 43. In this way, the fixing unit 12 can be pressed from the surface of the heating roller 35 by the user's hand while the lever tip 21B is pressed to stop the operation lever 21 at the roller pad separation operation position. The state where the surface of the pressure belt 47 is separated from the pressure pad 43 can be maintained. Therefore, the fixing unit 12 is, for example, a so-called jam in which the print medium 5 is jammed between the heating roller 35 and the pressure belt 47 (that is, the first sandwiching part NP1 and the second sandwiching part NP2) when a print image is formed. When the operation lever 21 is rotated to the roller pad separation operation position after the operation of the printer 1 is stopped, the pressure is applied together with the pressure roller 40 and the pressure pad 43 from the surface of the heating roller 35. By separating the surface of the belt 47, the jammed print medium (hereinafter also referred to as jammed medium) 5 can be easily removed. Then, when the operation lever 21 is rotated to the roller pad separation operation position in this way, the fixing unit 12 is contracted to that extent when the hand holding the lever tip 21B is released. The left roller urging spring 63 and the right roller urging spring 64 are naturally extended so that the left roller supporting portion 41 and the right roller supporting portion 42 are rotated around the left rotating shaft 56 and the right rotating shaft 57. Rotate in the direction. Thus, the fixing unit 12 causes the left cam pressing plate 41BY and the right cam pressing plate 42BY to push the left one end side pressing portion 70A and the right one end side pressing portion 71A back in the other rotation direction, so that the left cam portion 70 and the right cam portion 71 are pushed back. Is rotated in the other rotation direction around the lever shaft 72, and the operation lever 21 is also rotated so as to push back from the roller pad separation operation position to the operation reference position in one rotation direction. Therefore, the fixing unit 12 can be applied again to the surface of the pressure roller 40 and the surface of the heating roller 35 only by releasing the hand from the operation lever 21 that has been rotated to the roller pad separation operation position (that is, the lever tip 21B). The first sandwiching part NP1 and the second sandwiching part NP2 can be formed by pressing the surface of the elastic layer 43D of the pressure pad 43 via the pressure belt 47. For this reason, the fixing unit 12 separates the surface of the pressure belt 47 together with the pressure roller 40 and the pressure pad 43 from the surface of the heating roller 35 when the print image is formed again after the jammed medium 5 is removed. Thus, it is possible to reliably prevent a print image from being formed on the surface of the print medium 5.

Further, as shown in FIGS. 15 and 16, the fixing unit 12 is, for example, manually operated by the user to rotate the operation lever 21 from the operation reference position to the other rotation direction (that is, the lever base 21 </ b> A after the operation reference posture). In response to this, the left cam portion 70 and the right cam portion 71 are also rotated in the other direction of rotation about the lever shaft 72. Thus, the fixing unit 12 presses the left other end side pressing portion 70B and the right other end side pressing portion 71B against the left cam pressing plate 41BY and the right cam pressing plate 42BY so that the left roller urging spring 63 and the right roller are attached. The left roller support portion 41 and the right roller support portion 42 can be rotated in the direction of one rotation about the left rotation shaft 56 and the right rotation shaft 57 while the force spring 64 is compressed. Then, for example, when the operation lever 21 is rotated to the roller separation operation position in the other rotation direction in which the operation lever 21 slightly tilts the lever base portion 21A to the rear side to make the roller separation operation posture. The left other end side pressing portion 70B and the right other end side pressing portion 71B of the left cam portion 70 and the right cam portion 71 are positioned at a height position substantially equal to the height position of the lever shaft 72, and the left cam pressing plate 41BY and The end surface of the left other end side pressing portion 70B and the end surface of the right other end side pressing portion 71B are abutted against the right cam pressing plate 42BY. At this time, the fixing unit 12 causes the left roller support portion 41 and the right roller support portion 42 to move to the left rotation shaft 56 and the right turn so that the left roller biasing spring 63 and the right roller biasing spring 64 that have been compressed are extended. The left cam pressing plate 41BY is urged so as to rotate in the other rotation direction about the moving shaft 57, but the urging force is received by the lever shaft 72 via the left cam portion 70 and the right cam portion 71. and abutting the end face and the end face of the right end side pressing portion 71B of the left end side pressing portion 70B for the right cam pressing plate 42BY to force the equilibrium. As a result, when the operation lever 21 is rotated to the roller separation operation position, the fixing unit 12 causes the left other end side pressing portion 70B and the right other end side pressing portion 71B of the left cam portion 70 and the right cam portion 71 to move to the left. The roller support part 41 and the right roller support part 42 can be locked in a state where the rotation is stopped at the rotation position at this time. The fixing unit 12 has a cam other end side length shorter than the cam one end length in the left cam portion 70 and the right cam portion 71, but also in this case, the rotation direction of the left roller support portion 41 and the right roller support portion 42 is one rotation direction. The pressure roller 40 can be moved away from the heating roller 35 by moving the pressure roller 40 in one rotation direction in accordance with the rotation. That is, in the fixing unit 12, the length of the other end of the cam is shorter than the length of the one end of the cam. Although the gap is narrower than when the lever 21 is rotated to the roller pad separation operation position, the lever 21 can be separated. At this time, the fixing unit 12 locks the rotation of the left roller support portion 41 and the right roller support portion 42 by the left cam portion 70 and the right cam portion 71, and accordingly, the pressure roller 40 is replaced with the heating roller 35. It can be locked away from. However, at this time, the fixing unit 12 is displaced in one rotation direction away from the heating roller 35 in accordance with the rotation of the left roller support portion 41 and the right roller support portion 42 in one rotation direction. Although the plurality of pad urging springs 60 are extended, the amount of displacement of the displacement restricting portion 46 according to the length of the other end of the cam is compared with the case where the operation lever 21 is rotated to the roller pad separation operation position. And can be made smaller. For this reason, the fixing unit 12 presses or closes the restriction surface one end portion and the restriction surface other end portion of the displacement restricting engagement portion 43AY of the pressure pad 43 to the tip portions of the left restriction claw portion 46B and the right restriction claw portion 46C. Thus, the entire surface of the elastic layer 43 </ b> D of the pressure pad 43 can be pressed against the surface of the heating roller 35 via the pressure belt 47. That is, since the fixing unit 12 extends the plurality of pad urging springs 60 as compared with the case where the operation lever 21 described above is positioned at the operation reference position without being rotated at all, The entire surface of the elastic layer 43D is pressed against the surface of the heating roller 35 via the pressure belt 47 with a predetermined third pressing force smaller than the second pressing force, and apparently the same pressing as that of the second sandwiching portion NP2. The part PR1 can be formed.

  In this way, the fixing unit 12 can be used for a certain period of time, such as when the printer 1 is shipped from the printer manufacturing factory, or when the user who purchased the printer 1 moves. When is not used, the pressure roller 40 can be kept separated from the heating roller 35 when the operation lever 21 is rotated to the roller separation operation position. Therefore, the fixing unit 12 applies the pressure belt 47 on the surface of the pressure roller 40 to the surface of the pressure roller 40 or the pressure belt 47 while the printer 1 (that is, the fixing unit 12) is not used. It is possible to prevent distortion from being caused by pressing the same portion against the surface of the heating roller 35 over a long period of time. In addition, when the operation lever 21 is rotated to the roller separation operation position, the fixing unit 12 keeps the entire surface of the elastic layer 43D of the pressure pad 43 even if the pressure roller 40 is kept separated from the heating roller 35. It can be kept pressed against the surface of the heating roller 35 via the pressure belt 47 with a substantially uniform third pressing force. For this reason, the fixing unit 12 is provided with the elasticity of the pressure pad 43, for example, immediately after the printer 1 is operated in a printer manufacturing factory and test printing is performed, or immediately after the user uses the printer 1 for forming a print image. Even when the operation lever 21 is rotated to the roller separation operation position in a state where the temperature of the layer 43D is relatively high, the entire surface of the elastic layer 43D of the pressure pad 43 is moved over the surface of the heating roller 35 via the pressure belt 47. The elastic layer 43D of the pressure pad 43 contracts due to natural cooling, and the curvature of the surface of the heating roller 35 is changed to the curvature of at least a part of the surface due to the residual distortion during molding. Therefore, it is possible to almost certainly prevent deformation by making it smaller. That is, the fixing unit 12 is configured so that, even when the operation lever 21 is rotated to the roller separation operation position when the elastic layer 43D of the pressure pad 43 is naturally cooled from a relatively high temperature to, for example, room temperature, the pressure pad 43 Since the elastic layer 43D can be naturally cooled while the entire surface of the elastic layer 43D of 43 is pressed against the surface of the heating roller 35 via the pressure belt 47, the elastic layer 43D is formed when a print image is formed. It is possible to restore the original shape by contracting by the amount of thermal expansion. Incidentally, when the operation lever 21 that has been rotated to the roller separation operation position is rotated to the operation reference position in one rotation direction, for example, the user pushes the lever tip 21B forward by the user by hand. Accordingly, the left cam portion 70 and the right cam portion 71 are also rotated in one rotation direction around the lever shaft 72. Thereby, the fixing unit 12 unlocks the rotation of the left roller support portion 41 and the right roller support portion 42 by the left other end side pressing portion 70B and the right other end side pressing portion 71B of the left cam portion 70 and the right cam portion 71. Then, the left roller supporting portion 41 and the right roller supporting portion 42 are rotated about the left rotating shaft 56 and the right rotating shaft 57 by the urging of the left roller urging spring 63 and the right roller urging spring 64. Can be rotated in the direction. Therefore, the fixing unit 12 again presses the surface of the pressure roller 40 and the surface of the elastic layer 43D of the pressure pad 43 against the surface of the heating roller 35 via the pressure belt 47, and the first sandwiching portion NP1 and the second sandwiching portion NP1. The sandwiching part NP2 can be formed.

  By the way, as shown in FIG. 17 in which the same reference numerals are assigned to the parts corresponding to FIG. 13, for example, the above-described left cam portion 70 and right cam portion 71 are used, although the configuration of the fixing unit 12 described above is partially used. The left cam portion and the right cam portion 80 have a shorter cam other end length than the plurality of pad urging springs 60 described above, and the plurality of pad urging springs 81 having different natural lengths, spring constants, and the like. If another fixing unit 82 in which some parts are changed to those different from those described above is configured, the fixing unit 82 described above is fixed when the operation lever 21 is positioned at the reference operation position. Similar to the unit 12, the surface of the pressure roller 40 and the surface of the elastic layer 43D of the pressure pad 43 can be pressed against the surface of the heating roller 35 via the pressure belt 47, and the operation lever 21 is low. When it is rotating operation to the pad separation operation position, it is possible to separate the surface of the pressure belt 47 with the pressure roller 40 and the pressure pad 43 from the surface of the above-described fixing unit 12 similarly to the heating roller 35. In the other fixing unit 82, for example, when the operation lever 21 is rotated from the reference operation position to the pad separation position in the other rotation direction and the rotation of the left roller support portion 41 and the right roller support portion 42 is locked, the above-described fixing is performed. Unlike the unit 12, while pressing the surface of the pressure roller 40 against the surface of the heating roller 35 via the pressure belt 47, the surface of the pressure belt 47 is slightly moved together with the pressure pad 43 from the surface of the heating roller 35. Can remain separated. As a result, in the other fixing unit 82, when the operation lever 21 is rotated to the pad separation position in this way, for example, an envelope thicker than one print medium 5 is transferred to the second sandwiching section and the first sandwiching section. By sequentially passing the toner image on the surface of the envelope, a print image such as the address can be formed.

  However, in the other fixing units 82, even if the operation lever 21 is rotated to the pad separation position, the pressure roller 40 cannot be separated from the heating roller 35. Must be rotated to the roller pad separation operation position. In another fixing unit 82, even if the operation lever 21 is rotated to the roller pad separation operation position, when the hand is released from the operation lever 21, the left roller biasing spring 63 and the right roller biasing spring 64 are attached. The left roller support portion 41 and the right roller support portion 42 are rotated in the other rotation direction by the force, and the surface of the pressure roller 40 and the surface of the elastic layer 43D of the pressure pad 43 are again pressed on the surface of the heating roller 35. It will be pressed through the belt 47. For this reason, in the other fixing unit 82, in order to maintain the separation state of the pressure roller 40 from the heating roller 35 even if the operation lever 21 rotated to the roller pad separation operation position is released, A lock piece 84 is required to lock the rotation of the lever 21 at the roller pad separation operation position. Here, as shown in FIG. 18, the lock piece 84 is provided with a substantially square block-like lever engaging portion 84B at the upper end of a substantially ship-shaped housing engaging portion 84A with their longitudinal directions orthogonal to each other. Yes. As shown in FIG. 19 in which the same reference numerals are assigned to the corresponding parts in FIG. 2 together with FIG. 17, the other fixing unit 82 locks, for example, near the front end in the lever operation opening 20CX of the unit housing 20. The casing engaging portion 84A of the piece 84 is inserted so that the longitudinal direction of the casing engaging portion 84A is substantially parallel to the printer left-right direction. In another fixing unit 82, the operation lever 21 is rotated to the roller pad separation operation position in one rotation direction, and the lever tip portion 21B is inserted below one end portion located on the rear side of the lever engagement portion 84B. After that, the hand is released from the lever tip 21B. As a result, the other fixing unit 82 causes the left roller supporting portion 41 and the right roller supporting portion 42 to be moved by the left roller biasing spring 63 and the right roller biasing spring 64 in response to the release of the hand from the lever tip 21B. The operation lever 21 is urged together with the left cam portion 70 and the right cam portion 71 to push back from the roller pad separation operation position to the operation reference position in the other rotation direction, but the end surface of the lever tip 21B is the lever of the lock piece 84. While engaging with one end of the engaging portion 84B from below, the left and right sides of the lever operation opening 20CX of the unit housing 20 are connected to one end of the housing engaging portion 84A and others. The end is pressed from the inside of the unit housing 20 to be engaged. In this way, the other fixing unit 82 locks the operation lever 21 that has been rotated to the roller pad separation operation position by the user by the lock piece 84 so that the rotation is stopped at the roller pad separation operation position. Even if the hand is released from the distal end portion 21B, the separation state of the pressure roller 40 with respect to the heating roller 35 can be maintained.

  However, in the other fixing unit 82, the lock piece 84 is used as described above to maintain the separation state of the pressure roller 40 with respect to the heating roller 35, so that the surface of the pressure roller 40 and the pressure belt 47 are distorted. Although the sticking can be prevented, the lock piece 84 needs to be stored so as not to be lost while the printer 1 is continuously used. The other fixing unit 82 uses the lock piece 84 to lock the rotation of the operation lever 21 at the roller pad separation operation position so that not only the pressure roller 40 but also the pressure pad 83 is separated from the heating roller 35. At this time, when the elastic layer 43D of the pressure pad 43 is naturally cooled from a relatively high temperature, the elastic layer 43D of the pressure pad 43 is deformed by making the curvature of the surface smaller than the curvature of the surface of the heating roller 35. there's a possibility that. On the other hand, the fixing unit 12 according to the present embodiment does not use the lock piece 84 and does not store it, and the left cam portion 70 and the right cam portion that are interlocked with the rotation operation of the operation lever 21 as described above. 71 can lock the rotation of the left roller support portion 41 and the right roller support portion 42 to maintain the state where the pressure roller 40 is separated from the heating roller 35, and during that time, the elastic layer of the pressure pad 43. About the surface of 43D, the state pressed against the surface of the heating roller 35 via the pressure belt 47 can be maintained. Therefore, the fixing unit 12 according to this embodiment has a simple configuration that does not require the lock piece 84 as compared with the other fixing units 82, and the surface of the pressure roller 40 and the pressure belt 47 are distorted. In addition, the elastic layer 43D of the pressure pad 43 can be prevented from being deformed by making the surface curvature smaller than that of the surface of the heating roller 35.

(1-3) Operation and Effect of Embodiment In the above configuration, in the printer 1, the heating roller 35 is provided in the fixing unit 12 so as to be rotatable. In the printer 1, the pressure roller 40 is rotatably provided in the fixing unit 12, and a pressure pad 43 having an elastic layer 43 </ b> D is urged toward the heating roller 35. A pressure belt 47 is stretched around the pad 43, and the entire surface of the pressure roller 40 and the elastic layer 43 </ b> D of the pressure pad 43 are pressed against the surface of the heating roller 35 via the pressure belt 47. The insertion part NP1 and the 2nd clamping part NP2 were formed. Therefore, when forming the print image, the printer 1 transfers the toner image to the surface of the print medium 5 and then sandwiches the print medium 5 by the fixing unit 12 in order between the second sandwiching part NP2 and the first sandwiching part NP1. By heating and pressing while being conveyed, the toner image can be fixed on the surface of the print medium 5 to form a print image. In addition, in the printer 1, the fixing unit 12 is provided with a separation control unit 73 having an operation lever 21 that can be rotated. When the operation lever 21 is rotated from the operation reference position to the roller separation operation position in the fixing unit 12, the printer 1 covers the entire surface of the elastic layer 43 </ b> D of the pressure pad 43 through the pressure belt 47. The pressure roller 40 is separated from the heating roller 35 while being pressed against the surface of the surface 35. According to the above configuration, when the printer 1 is not used for a certain period of time, such as shipping from a printer manufacturing factory or transportation or storage associated with the moving of a user, the fixing unit 12 precedes the transportation or storage. When the operation lever 21 is rotated from the operation reference position to the roller separation operation device, the surface of the pressure roller 40 or the pressure belt 47 is heated to the heating roller 35 via the pressure belt 47 on the surface of the pressure roller 40. It is possible to prevent distortion from being caused by pressing the same portion against the surface for a long period of time. At this time, in the printer 1, the operation lever 21 moves from the operation reference position to the roller separation operation device while the temperature of the elastic layer 43 </ b> D of the pressure pad 43 is relatively high as the toner image is heated and pressed in the fixing unit 12. The entire surface of the elastic layer 43D of the pressure pad 43 is heated via the pressure belt 47 even when the elastic layer 43D of the pressure pad 43 is naturally cooled during transportation or storage because of the rotation operation. By being pressed against the surface of the roller 35, it is possible to almost certainly prevent the elastic layer 43D from being deformed by contraction due to natural cooling so that the curvature of the surface is smaller than the curvature of the surface of the heating roller 35. For this reason, the printer 1 passes the surface of the pressure roller 40 and the entire surface of the elastic layer 43D of the pressure pad 43 again through the pressure belt 47 through the pressure belt 47 for transportation and storage. Is pressed against the surface of the heating roller 35 via the pressing belt 47 by the elastic layer 43D of the pressing pad 43 (that is, the pressing belt against the roller side second pressing portion of the heating roller 35). It is possible to almost certainly avoid the pressing force of the second belt side pressing portion 47) from becoming uneven. Therefore, even when the printer 1 heats and pressurizes the toner image on the surface of the print medium 5 by the fixing unit 12, the fixing position of the toner image on the surface of the print medium 5 or a fixing defect that easily peels off may occur. Thus, it is possible to prevent the deterioration of the quality of the printed image.

In the printer 1, the fixing unit 12 uses the pressure belt 47 formed without providing an elastic layer for fixing the toner image on the surface of the print medium 5. Therefore, in the printer 1, when the operation lever 21 is rotated from the operation reference position to the roller separation operation position, the surface of the elastic layer 43 </ b> D of the pressure pad 43 is pressed against the surface of the heating roller 35 via the pressure belt 47. even if the left, the pressure belt 47, the Ibitsukuse stick by pressing of the heating roller 35 by the elastic layer 43D of the press pad 43 can be reduced as much as possible. In addition, the printer 1 is provided with a left roller support portion 41 and a right roller support portion 42 that rotatably support the pressure roller 40 in the fixing unit 12 so that the pressure roller 40 can be rotated. When the operation lever 21 is rotated from the operation reference position to the roller separation operation position when the operation lever 21 is rotated integrally with the operation lever 21 to rotate the left roller support portion 41 and the right roller support portion 42, the left roller The left cam portion 70 and the right cam portion 71 that lock the rotation to stop the rotation of the support portion 41 and the right roller support portion 42 are provided. Therefore, the printer 1 can be heated only by rotating the operation lever 21 from the operation reference position to the roller separation operation position without using a separate part such as a lock piece that stops and locks the operation lever 21. The pressure roller 40 can be separated from the roller 35 and the separated state can be maintained. Further, in the printer 1, the left roller support portion 41 and the right roller support portion 42 that support the pressure pad 43 are rotatably provided on the left roller support portion 41 and the right roller support portion 42, and the operation lever 21 is moved from the operation reference position. When the roller pad separation operation position is rotated, the left roller support portion 41 and the right roller support portion 42 are rotated via the left cam portion 70 and the right cam portion 71 in response to the rotation operation. The pressure belt 47 is spaced apart from the pressure pad 40 and the pressure pad 43. Accordingly, the printer 1 not only operates the operation lever 21 to prevent the surface of the pressure roller 40 and the pressure belt 47 from being distorted, but also jams between the heating roller 35 and the pressure belt 47. Even when the operation lever 21 is operated, the pressure belt 47 is separated from the heating roller 35 together with the pressure roller 40 and the pressure pad 43, so that the jammed medium 5 can be easily removed. The usability of the printer 1 together with the fixing unit 12 can be greatly improved. Further, the printer 1 biases the left roller support portion 41 and the right roller support portion 42 so as to rotate, thereby biasing the pressure roller 40 toward the heating roller 35 and the right roller biasing spring 63 and the right roller biasing force. Even if the operation lever 21 is rotated from the operation reference position to the roller pad separation operation position, for example, when the hand is released from the operation lever 21, the left roller biasing spring 63 and the right roller biasing spring are provided. 64, the left roller support portion 41 and the right roller support portion 42 are rotated to push the operation lever 21 back to the operation reference position, and the surface of the pressure roller 40 and the surface of the elastic layer 43D of the pressure pad 43 are moved. The first sandwiching part NP1 and the second sandwiching part NP2 are formed by pressing against the surface of the heating roller 35 via the pressure belt 47. Therefore, the printer 1 can fix the toner image on the surface of the print medium 5 when the operation lever 21 is rotated from the operation reference position to the roller pad separation operation position and the jammed medium 5 is removed in the fixing unit 12. The pressure belt 47 is separated from the heating roller 35 together with the pressure roller 40 and the pressure pad 43 because the state can be easily returned to the state and such a return can be realized simply by releasing the hand from the operation lever 21. It is also possible to prevent the toner image from being fixed on the surface of the print medium 5 together with the formation of the print image. In addition to this, the printer 1 operates the operation lever 21 with the operation reference when separating only the pressure roller 40 from the heating roller 35 and when separating the pressure roller 40 and the pressure pad 43 from the heating roller 35. Rotation operation was performed from the position to the roller separation operation position and roller pad separation operation position in opposite directions. Therefore, the printer 1 operates the single operation lever 21 for separating only the pressure roller 40 from the heating roller 35 and for separating the pressure roller 40 and the pressure pad 43 from the heating roller 35. They can be easily distinguished, and can be rotated by reducing erroneous operations as much as possible.

(2) Other embodiments (2-1) Other embodiments 1
In the above-described embodiment, the case where the fixing unit according to the present invention is applied to the fixing unit 12 provided in the direct transfer type monochrome printer 1 described above with reference to FIGS. 1 to 16 has been described. . However, the present invention is not limited to this. The fixing unit in which the heating unit 30 and the pressurizing unit 31 are arranged upside down from the above-described embodiment, a heater that is a halogen lamp, and a plate that has a resistance wire for heat generation. In addition to being provided in the heating roller 35, or not in the heating roller 35, various kinds of at least one heater such as a heater in the shape of the heater, or in the pressure roller 40 and when the fixing unit provided so as to incorporate the belt guide, a fixing unit for heating the heater by induction heating method, operation lever 21 is rotationally operated from the operation reference position to the roller separation operation position, such as lock piece The rotation of the operation lever 21 is locked using a lock part, and the rotation of the left roller support part 41 and the right roller support part 42 is locked in accordance with this, and pressurization is performed. As such a fixing unit which locks only over La 40 in spaced apart condition from the heating roller 35, it can be widely applied to the fixing unit of various other configurations. The present invention is provided a printer or for color of direct transfer method, the secondary transfer scheme for color printer, MFP (Multi-Function Peripheral) , a facsimile, a complex machine, a variety of image forming apparatus such as a copier It can also be applied to a fixing unit.

(2-2) Other embodiment 2
In the above-described embodiment, the case where the image forming apparatus according to the present invention is applied to the direct transfer type monochrome printer 1 described above with reference to FIGS. 1 to 16 has been described. However, the present invention is not limited to this, and various other configurations such as a direct transfer type color printer, a secondary transfer type color printer, an MFP, a facsimile, a multifunction peripheral, a copying machine, and the like. The present invention can be widely applied to image forming apparatuses.

(2-3) Other Embodiment 3
Further, in the above-described embodiment, the case where the heating roller 35 described above with reference to FIGS. 1 to 16 is applied as the heating rotator for heating the medium has been described. However, the present invention is not limited to this, and the surface of the print medium 5 is received by the heat of the heating roller provided near the surface without the heaters 36 and 37 provided therein or the heater provided in the pressure unit. A wide variety of other heating rotators such as a heating roller for heating the toner image, a heater provided inside or outside, and an endless belt stretched between the roller and the belt guide. Can do.

(2-4) Other Embodiment 4
Further, in the above-described embodiment, the case where the pressure belt 47 described above with reference to FIGS. 1 to 16 is applied as the belt for sandwiching the medium together with the heating rotator has been described. However, the present invention is not limited to this, and the direction of approaching the heating roller 35 between the heating roller 35 and the pressure pad 43 and the pressure roller 40 so as to sandwich the print medium 5 together with the heating roller 35. Various belts having various configurations can be widely applied, such as a belt-like belt arranged so as to be displaceable in a direction away from the belt.

(2-5) Other Embodiment 5
Further, in the above-described embodiment, the case where the pressure roller 40 described above with reference to FIGS. 1 to 16 is applied as the pressure rotator that pushes the belt in the direction of the heating rotator has been described. However, the present invention is not limited to this, such as a pressure roller provided with a heater inside, or an endless belt provided with a heater inside or outside and stretched between the roller and a belt guide. Various other types of pressure rotators can be widely applied.

(2-6) Other embodiment 6
Further, in the above-described embodiment, the additional portion described above with reference to FIGS. 1 to 16 is used as a pressure pad that has an elastic portion having a bending paired with the bending of the heating rotator and pushes the belt toward the heating rotator. The case where the pressure pad 43 is applied has been described. However, the present invention is not limited to this, and an elastic portion formed so as to be partially different in hardness by combining two or more types of elastic members having different hardness while having a bending paired with the bending of the heating rotating body. Various other configurations of pressure pads can be widely applied, such as the provided pressure pads.

(2-7) Other Embodiment 7
Further, in the above-described embodiment, the separation control having the operation lever 21 that can be rotated as described above with reference to FIGS. 1 to 16 as the moving unit that moves the pressure rotator and the pressure pad in accordance with the operation of the operation unit. The case where the unit 73 is applied has been described. However, the present invention is not limited to this, and has a separation control unit capable of operating the operation lever 21 only to the roller separation operation position, a separation control unit having a lock part such as a lock piece, and an operation unit capable of pressing operation. A moving unit that moves the pressure rotator and the pressure pad according to the pressing operation of the operation unit, and an operation unit that can be slid, and the pressure rotator and the pressure according to the slide operation of the operation unit. Various other moving parts such as a moving part for moving the pad can be widely applied.

(2-8) Other embodiment 8
Further, in the above-described embodiment, a predetermined operation state with respect to the operation unit is maintained, the state in which the pressing rotary member is moved in the direction away from the heating rotary member by the moving unit, and the belt is provided by the press pad. As described above, the left cam portion 70 and the right cam portion 71 described above with reference to FIGS. However, the present invention is not limited to this, and various other types of holding parts such as a lock part such as a lock piece can be widely applied.

(2-9) Other Embodiment 9
Further, in the above-described embodiment, the left roller support portion 41 and the right roller support portion 42 described above with reference to FIGS. 1 to 16 and the left pad support portion as the support portions that support the pressure rotating body and the pressure pad. The case where 44 and the right pad support part 45 are applied has been described. However, the present invention is not limited to this, like the left roller support 41 and the right roller support 42 that support the pressure roller 40, and the left and right plates 25 and 26 of the unit frame 28 that support the pressure pad 43. In addition, the support portions having various configurations can be widely applied.

(2-10) Other Embodiment 10
Further, in the above-described embodiment, the pressure pad and the pressure rotator are used as the urging unit that urges the support unit so as to push the belt in the direction of the heating rotator. The case where the roller biasing spring 63 and the right roller biasing spring 64 are applied has been described. However, the present invention is not limited to this, and various other urging portions such as a torsion spring and a leaf spring can be widely applied.

  The present invention can be used for an image forming apparatus such as a printer, an MFP, a facsimile machine, a multifunction peripheral, and a copying machine, and a fixing unit provided in the image forming apparatus.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 12 ... Fixing unit, 21 ... Operation lever, 30 ... Heating part, 31 ... Pressure part, 35 ... Heating roller, 36, 37 ... Heater, 40 ... Pressure roller, 41 …… Left roller support portion, 42 …… Right roller support portion, 43 …… Pressure pad 43, 43D …… Elastic layer, 44 …… Left pad support portion, 45 …… Right pad support portion, 47 …… Addition Pressure belt, 60 ... Pad biasing spring, 63 ... Left roller biasing spring, 64 ... Right roller biasing spring, 70 ... Left cam portion, 71 ... Right cam portion, 72 ... Lever shaft, 73 …… Separation control unit.

Claims (5)

A fixing unit that heats and fixes a developer image on the surface of a medium,
A heating rotator for heating the medium;
A belt for sandwiching the medium together with the heating rotating body;
A pressure rotator that pushes the belt in the direction of the heating rotator;
A pressure pad that has an elastic part having a bending paired with the bending of the heating rotator, and presses the belt in the direction of the heating rotator;
A moving unit that moves the pressurizing rotating body and the pressurizing pad in accordance with an operation of the operating unit;
When the operating unit is operated to the rotating body separation operation position, while holding the operation section in the rotary body separation operation position, it holds the previous SL pressure rotating bodies separated state from the heating rotating body, It said pressure pad, comprising a holding portion for holding the belt at a position contacting with the heating rotating body,
The moving unit is
When the operation unit is operated to the rotating body separation operation position when the unit is not used for a predetermined period, the pressure rotation is performed while the belt is brought into contact with the heating rotating body by the pressure pad. The body is moved away from the heating rotator to be in a separated state, and when the jammed medium is removed from the unit, the operation unit is operated to a rotating body pad separating operation position different from the rotating body separating operation position. Then, the pressure pad and the pressure rotator are moved away from the heating rotator to be separated from each other.
Fixing unit. A support portion for supporting the pressure rotator and the pressure pad;
An urging portion that urges the support portion so that the pressure pad and the pressure rotator are pushed in the direction of the heating rotator;
The operation unit is
It is provided so that it can be rotated from the operation reference position,
The moving unit is
While the operation unit rotated to the rotating pad separation operation position is pressed by hand, the pressing pad and the pressing rotating body are moved away from the heating rotating body to be in a separated state , When the hand is released from the operation unit, the operation unit is returned to the operation reference position according to the urging of the support unit by the urging unit, and the pressure pad and the pressure rotating body are The fixing unit according to claim 1 , wherein the belt is moved so as to be pushed toward the heating rotator. The operation unit is
The fixing unit according to claim 2 , wherein the fixing unit can be rotated from the operation reference position to the rotating body separating operation position and the rotating pad separating operation position in opposite directions. A fixing unit that heats and fixes a developer image on the surface of a medium,
A heating rotator for heating the medium;
A belt for sandwiching the medium together with the heating rotating body;
A pressure rotator that pushes the belt in the direction of the heating rotator;
A pressure pad that has an elastic part having a bending paired with the bending of the heating rotator, and presses the belt in the direction of the heating rotator;
A moving unit that moves the pressurizing rotating body and the pressurizing pad in accordance with an operation of the operating unit;
The operation unit is held in a predetermined operation state, and the moving unit is held in a separated state in which the pressure rotating body is moved away from the heating rotating body, and the pressure pad is attached to the belt. A holding unit that holds the heating rotating body at a position in contact with the heating rotating body;
A support portion for supporting the pressure rotator and the pressure pad;
An urging portion that urges the support portion so that the pressure pad and the pressure rotator are pushed toward the heating rotator.
With
The operation unit is
It is provided so that it can be rotated from the operation reference position,
The moving unit is
When the operation unit is operated from the operation reference position to the rotating pad separation operation position, while the operation unit rotated to the rotating pad separation operation position is pressed by hand, the pressure pad and When the pressure rotator is moved away from the heating rotator and the hand is released from the operation unit, the operation unit is moved to the operation reference according to the urging of the support unit by the urging unit. While returning to the position, the pressure pad and the pressure rotator are moved so as to push the belt toward the heating rotator.
Fixing unit. The image forming apparatus according to claim 1, further comprising the fixing unit.

Images