JP2015028558A - Fixing apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus configured to prevent heat dissipation even when a thin heat roller is used, to prevent reduction in temperature of an outer periphery of the heat roller, thereby allowing continuous fixing operation without increasing the amount of heat applied, and to provide an image forming apparatus.SOLUTION: A fixing apparatus 18 includes a heat roller 38 and a pressure roller 39. An internal space 51 of the heat roller 38 is shielded from the outside, to prevent air from flowing in and out. An internal shielding part 53 is formed in the internal space 51, to form a gap 60 between the internal shielding part 53 and an outer periphery 38A of the heat roller 38. A heating unit 55 is supported by the internal shielding part 53, to heat the outer periphery 38A from the inside.

Description

  The present invention relates to a fixing device that heats and fixes toner transferred to a recording medium, and an image forming apparatus including the same.

  An electrophotographic image forming apparatus includes a fixing device that fixes a toner image transferred to a printing paper (recording medium) onto the printing paper. The fixing device includes a heating device such as a heater, a heat roller heated by the heating device, and a pressure roller driven by being brought into pressure contact with the heat roller. The heat roller is rotatably supported by the fixing device, and is rotated by a rotational driving force transmitted from an electric motor such as a motor. When printing paper is transported to the nip formed between the heat roller and pressure roller, heat is transferred from the heat roller to the toner image on the printing paper while the printing paper is being transported by the heat roller and pressure roller. The toner constituting the toner image is melted. The melted toner is fixed on the printing paper by the pressure applied by the pressure roller.

  In this type of fixing device, when the image forming apparatus is in a power saving mode (also referred to as a sleep mode), the heating device is stopped or the heating temperature by the heating device is lowered. In addition, when the power of the image forming apparatus is turned off, the heating device is naturally stopped. In this case, the temperature of the heat roller is lower than a predetermined fixing temperature at which the toner can be fixed. On the other hand, when the image forming apparatus returns from the power saving mode or when the power of the image forming apparatus is turned on, heating by the heating device is resumed and the temperature of the heat roller is raised to the fixing temperature. Such an operation is called warm-up, and the time required for warm-up is called warm-up time.

  Conventionally, a thin heat roller having a small heat capacity is used in an image forming apparatus in order to shorten the warm-up time and shorten the time until a fixing operation is possible. In this case, since the amount of material on the outer peripheral portion of the heat roller to be heated is small, when heated by the heating device, the heat roller is raised to the fixing temperature relatively quickly. However, the thin heat roller has a small heat capacity. Therefore, for example, when a fixing operation is continuously performed on a large number of printing papers, heat is taken away at each fixing operation, and in some cases, the outer peripheral portion of the heat roller maintains the fixing temperature. I can't do that. With respect to such problems, a device that heats the heat roller with a plurality of heating devices (Patent Documents 1 and 2), and a device that suppresses heat conduction other than the nip portion between the heat roller and the pressure roller (Patent Document 3). It has been known.

JP 09-204114 A Japanese Patent Application Laid-Open No. 11-258942 JP 2009-156901 A

  However, since Patent Documents 1 and 2 heat the heat roller with a plurality of heating devices, the power consumption is large and the power saving effect is significantly reduced. Moreover, the structure of patent document 3 forms a some heat shield hole in the outer peripheral part of a heat roller. Therefore, the air warmed inside the heat roller is discharged from the heat shield hole, so that heat is wasted with the air.

  The present invention has been made in view of the above circumstances, and its purpose is to suppress the release of heat and reduce the temperature of the outer peripheral portion of the heat roller even when a thin heat roller is used. An object of the present invention is to provide a fixing device capable of performing a continuous fixing operation without increasing the amount of heating by suppressing it, and an image forming apparatus including the fixing device.

  A fixing device according to one aspect of the present invention includes a heat roller, an internal blocking unit, and a heating unit. The heat roller has an internal space shielded from the outside, and transfers heat to the toner transferred to the recording medium by contacting the recording medium while rotating. The internal blocking part is provided in the internal space of the heat roller, and forms a gap with the outer peripheral part of the heat roller. The heating part is supported by the internal blocking part and heats the outer peripheral part from the inside.

  An image forming apparatus according to another aspect of the present invention includes an image forming unit that transfers an image of toner onto a recording medium, and the above-described fixing device.

  This Summary is provided to introduce a selection of concepts in a simplified form that are appropriate for the following detailed description, with reference where appropriate to the accompanying drawings. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter. . Furthermore, the claimed subject matter is not limited to embodiments that solve any or all disadvantages noted in any part of this disclosure.

  According to the present invention, even if a thin-walled heat roller is used, it suppresses the release of heat and suppresses the decrease in the temperature of the outer peripheral portion of the heat roller, thereby continuing without increasing the heating amount. It is possible to perform a fixing operation.

1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of a fixing device provided in the image forming apparatus illustrated in FIG. 1. It is a figure which shows the structure of the heat roller with which the fixing apparatus shown in FIG. 2 is provided. It is a figure which shows the structure of the internal interruption | blocking part provided in the heat roller shown in FIG.

  Embodiments of the present invention will be described below with reference to the drawings as appropriate.

[Image forming apparatus 10]
FIG. 1 is a schematic diagram showing a configuration of an image forming apparatus 10 (an example of the image forming apparatus of the present invention) according to an embodiment of the present invention. The image forming apparatus 10 forms an image on the printing paper S based on the read image data of the original or image data input from the outside. As shown in FIG. 1, the image forming apparatus 10 includes a scanner 12 that reads an image of a document and an electrophotographic image forming unit 14. The scanner 12 is provided in the upper part of the image forming apparatus 10, and the image forming unit 14 is provided in the lower part of the image forming apparatus 10. A specific example of the image forming apparatus 10 according to the embodiment of the present invention is a printer, a copier, a facsimile, or a multifunction machine having these functions.

  The image forming unit 14 forms an image on the printing paper S based on a print job such as image data read by the scanner 12 or image data input from the outside. The image forming unit 14 mainly controls the paper feed tray 16, the transport roller 19, the transfer device 15, the fixing device 18 (an example of the fixing device of the present invention), the operation display unit 17, and these operations. And a control unit (not shown). These components are arranged inside a casing 20 that constitutes a housing of the image forming unit 14. The paper feed tray 16 is configured to hold a plurality of print sheets S. The transfer device 15 transfers the toner image onto the surface of the printing paper S fed from the paper feed tray 16. The fixing device 18 fixes the toner image transferred onto the printing paper S to the printing paper S.

  The control unit performs control to switch the operation mode of the image forming apparatus 10 to either the normal mode or the power saving mode (sleep mode). Here, the normal mode is an operation mode in which an image forming operation in the image forming apparatus 10 is immediately set to be executable when an image forming instruction is input. Specifically, the control unit controls the heating of the heat roller 38 in the fixing device 18 so as to reach a predetermined fixing temperature at which the toner can be fixed. The power saving mode refers to heating control so that the temperature of the heat roller 38 is lower than the fixing temperature when an image formation instruction is not input within a predetermined time, or a fixing device. 18 is an operation mode in which heating at 18 is stopped. Note that switching of operation modes and each operation mode in the image forming apparatus 10 are well known, and thus detailed description thereof is omitted in the present embodiment.

  Between the upper part of the casing 20 and the scanner 12, a paper discharge space 21 that is open at the front is provided. A paper discharge tray 23 is provided on the lower surface of the paper discharge space 21. The printing paper S fed from the paper feed tray 16 is transported by a transport roller 19 along a transport path 20A provided in the casing 20, and a toner image is formed on the printing paper S by the transfer device 15 in the transport process. Transcribed. The toner image transferred to the printing paper S is fixed to the printing paper S by being heated and melted when passing through the fixing device 18. The printing paper S that has passed through the fixing device 18 is discharged into the paper discharge space 21 and held on the paper discharge tray 23.

[Fixing device 18]
The fixing device 18 includes a frame 34, a heat roller 38 (an example of the heat roller of the present invention), a pressure roller 39 (an example of the pressure roller of the present invention), and a temperature sensor 44.

  As shown in FIG. 2, both the heat roller 38 and the pressure roller 39 are formed in a cylindrical shape that is long in the depth direction of the image forming apparatus 10 (direction perpendicular to the paper surface of FIG. 2). That is, the pressure roller 39 is provided in parallel to the heat roller 38. The heat roller 38 and the pressure roller 39 are rotatably supported by the frame 34. The pressure roller 39 is supported in a state of being pressed against the heat roller 38. Therefore, a nip portion 82 that can hold the printing paper S at the pressure contact point between the heat roller 38 and the pressure roller 39 is formed. A rotational driving force of a motor (not shown) is input to the rotation shaft 58 (see FIG. 3) of the heat roller 38. Thereby, the heat roller 38 is rotated. Further, the pressure roller 39 is also rotated following the rotation of the heat roller 38.

  As shown in FIG. 2, an internal space 51 is formed inside the heat roller 38. The internal space 51 is shielded from the outside by an outer peripheral portion 38 </ b> A constituting the roller surface of the heat roller 38 so that air cannot enter and exit. That is, the heat roller 38 has an internal space 51 that is shielded from the outside. The outer peripheral portion 38A is made of a hard material such as metal and has heat resistance that is strong against heat. As shown in FIG. 3, a rotation shaft 58 is provided at the center of the side wall 38B at both ends in the longitudinal direction of the outer peripheral portion 38A. The rotating shaft 58 is rotatably supported by the frame 34. When a rotational driving force from a motor (not shown) is input to the rotation shaft 58, the heat roller 38 rotates around the rotation shaft 58 in the rotation direction 30 shown in FIG. 2 (clockwise rotation direction in FIG. 2). As a result, the heat roller 38 conveys the print paper S while sandwiching the print paper S while contacting the print paper S at the nip portion 82 while rotating together with the pressure roller 39. In this conveyance process, heat is transmitted to the toner on the printing paper S from a heat roller 38 heated by a heating unit 55 described later. As a result, the toner is fixed on the printing paper S. The rotation shaft 58 is formed with a through hole 59 in the central axis direction. A support shaft 63 of the internal blocking portion 53 described later is inserted through the through hole 59.

  As shown in FIG. 2, the internal space 51 of the heat roller 38 is provided with an internal blocking portion 53 (an example of the internal blocking portion of the present invention) and a heating portion 55 (an example of the heating portion of the present invention). ing.

  The internal blocking portion 53 forms a gap 60 between the outer peripheral portion 38 </ b> A of the heat roller 38. Specifically, the internal blocking part 53 includes a casing 62 made of metal or resin, and a heat insulating material 64 filled in the casing 62. Support shafts 63 for supporting the internal blocking portion 53 are provided at both ends in the longitudinal direction of the housing 62. The support shaft 63 is inserted through the through hole 59 of the rotation shaft 63 of the heat roller 38. The support shaft 63 is exposed to the outside in the axial direction of the rotation shaft 58 from the through hole 59, and the exposed support shaft 63 is fixed to an internal frame (not shown) of the image forming apparatus 10. Thereby, the internal interruption | blocking part 53 is always fixed in the fixed position, without affecting the rotation operation of the heat roller 38, and rotating. A rubber ring-shaped sealing member is interposed in the gap between the support shaft 63 and the through hole 59 so that air in the internal space 51 does not leak out from the through hole 59.

  The heat insulating material 64 is for suppressing heat transfer (heat conduction). When the heat of the air in the gap 60 heated by the heating unit 55 described below is conducted to the inside of the housing 62, the temperature of the gap 60 is lowered. Thereby, the temperature change (temperature decrease) of the outer peripheral portion 38A of the heat roller 38 increases. Therefore, the heat insulating material 64 is provided inside the housing 62. This prevents the heat of the air in the gap 60 from being transmitted to the inside of the housing 62. As the heat insulating material 64, for example, a fiber heat insulating material such as glass wool or rock wool can be applied. In addition, a configuration in which the inside of the housing 62 is hollow and a gas (such as air) having a high heat insulating effect is filled, or a configuration in which the internal cavity is evacuated can be applied.

  The housing 62 includes an arc-shaped curved surface portion 66 and a recessed portion 68. The curved surface portion 66 has a curved surface that is spaced apart from the inner surface of the outer peripheral portion 38 </ b> A of the heat roller 38. The curved surface portion 66 forms a gap 60 with a constant distance from the outer peripheral portion 38A.

  The recessed portion 68 forms a space that encloses a heating portion 55 described later. Specifically, the recessed portion 68 is recessed from the curved surface portion 66 to the inside of the housing 62, and is formed in a generally arc shape. The recessed portion 68 is formed along the rotation axis direction of the heat roller 38. The heating unit 55 is accommodated in the recessed portion 68. In other words, the heating part 55 is included in the recessed part 68.

  As shown in FIG. 2, the recessed portion 68 is provided at a position P that is separated from the nip portion 82 by a predetermined angle θ toward the upstream side in the rotation direction 30 of the heat roller 38. The nip portion 82 is a pressure contact point between the heat roller 38 and the pressure roller 39. Therefore, the position P is a position separated from the pressure contact by an angle θ. The heating part 55 is accommodated in the recessed part 68 provided at such a position P.

  The heating part 55 heats the outer peripheral part 38A of the heat roller 38 from the inside. The heating unit 55 is, for example, a halogen heater that is long in the longitudinal direction of the heat roller 38. Of course, the heating unit 55 may be a heater other than the halogen heater. The heating unit 55 radiates heat to the inner surface of the outer peripheral portion 38A to heat the outer peripheral portion 38A. As described above, the heating unit 55 is accommodated in the recessed portion 68. Specifically, the heating unit 55 is supported by the internal blocking unit 53 while being accommodated in the recessed portion 68. In this embodiment, the heating part 55 is accommodated in the recessed part 68 provided in the position P. Therefore, the heating unit 55 heats the heated region 70 of the outer peripheral portion 38 </ b> A corresponding to the recessed portion 68. Specifically, the heating unit 55 radiates heat to the heated region 70 that is separated from the nip portion 82 by an angle θ toward the upstream side in the rotation direction 30 of the heating roller 38 at the outer peripheral portion 38A of the heating roller 38. The heated area 70 is heated. That is, the heating unit 55 is supported by the internal blocking unit 53 at the position P corresponding to the heated region 70. Here, the angle θ is set to an angle at which the nip portion 82 can maintain a temperature sufficient to fix the toner when the heated region 70 is heated by the heating portion 55. This angle θ is set to an angle corresponding to factors such as the outer diameter of the heat roller 38, the rotation speed, the heat capacity of the outer peripheral portion 38A, the volume of the gap 60, and the like.

  As shown in FIG. 4, the housing 62 has a pair of arm portions 74. The arm portion 74 is provided on each of the side walls 65 of the housing 62. In FIG. 4, the configuration provided on the side wall 65 on one side is shown, and the illustration of the arm portion 74 on the other side is omitted. In FIG. 4, the support shaft 63 is not shown for convenience of explanation. The arm portion 74 extends from the side wall 65 to the recessed portion 68 side. The arm portion 74 is a plate-like member made of a conductive material such as SUS or phosphor bronze that can conduct electricity. The arm portion 74 includes a parallel portion 74A parallel to the side wall 65 extending from the vicinity of the support shaft 62 toward the recessed portion 68, and a vertical portion 74B perpendicular to the side wall 65 from the end portion on the support shaft 62 side of the parallel portion 74A. It is configured. The parallel portion 74A is fixed to the side wall 65 by a fastener such as a screw or an adhesive material. An insulating sheet or the like is interposed between the parallel part 74A and the side wall 65.

  The end of the parallel portion 74 </ b> A on the recessed portion 68 side is fixed to the electrode 56 provided at the end of the heating portion 55 in the longitudinal direction. Thereby, the heating part 55 is supported by the pair of arm parts 74 in a state of being accommodated in the recessed part 68. The end of the parallel portion 74 </ b> A on the recessed portion 68 side is electrically connected to the electrode 56. A connector 76 for supplying power to the heating unit 55 is connected to the end of the vertical portion 74B. The connector 76 is connected to a power supply circuit (not shown). Thereby, the electric power for heating the heating part 55 is supplied to the heating part 55 through the connector 76, the arm part 74, and the electrode 56 from the said power supply circuit.

  As described above, since the fixing device 18 is configured, when the heated area 70 is heated by the heating unit 55, not only the heated area 70 is heated, but also the air in the gap 60 is radiated by the radiant heat. Heated. Since the internal space 51 of the heat roller 38 is shielded so that air does not enter from the outside, the warmed air in the gap 60 does not leak to the outside. Further, the heat of the air in the gap 60 is not transmitted to the inside of the internal blocking part 53 by the housing 62. For this reason, the temperature in the gap 60 is not wasted and is not significantly reduced. This makes it difficult for the heat of the outer peripheral portion 38A of the heat roller 38 to be taken away by the air in the gap 60, and even if the temperature of the outer peripheral portion 38A decreases after fixing, The temperature drop of the portion 38A is suppressed. As a result, since the temperature of the outer peripheral portion 38A does not extremely decrease every time the fixing operation is performed, even when the fixing operation is continuously performed on the plurality of printing sheets S, the heating amount is not increased. The heating roller 38 can be heated and controlled to a temperature at which fixing can be performed. Further, since the heat release from the outer peripheral portion 38A of the heat roller 38 is suppressed, the thin heat roller 38 having a small heat capacity can be used. As a result, when the image forming apparatus 10 returns from the power saving mode, Even when the power is turned on, the temperature of the heat roller 38 can be rapidly raised to a temperature at which the heat roller 38 can be fixed.

  In the above-described embodiment, the image forming apparatus 10 including the fixing device 18 is illustrated as an embodiment of the present invention. However, the present invention is of course applicable to a single product including only the fixing device 18.

  Since the scope of the present disclosure is defined not by the detailed description preceding the description of the claims but by the description of the appended claims, the embodiments described herein are merely exemplary and non-limiting I want to be understood. Therefore, all the changes which do not deviate from a claim, or an equivalent are included in a claim.

10: Image forming apparatus 18: Fixing apparatus 38: Heat roller 39: Pressure roller 51: Internal space 53: Internal blocking part 55: Heating part 60: Air gap 62: Housing 64: Heat insulating material 68: Recessed part 70: Heated area 74: Arm part 82: Nip part

Claims (5)

A heat roller having an internal space shielded from the outside and transferring heat to the toner transferred to the recording medium by contacting the recording medium while rotating;
An internal blocking part that is provided in the internal space of the heat roller and forms a gap with the outer periphery of the heat roller;
And a heating unit that is supported by the internal blocking unit and heats the outer peripheral part from the inside. A pressure roller provided in parallel with the heat roller and rotatable in a state of being pressed against the heat roller;
The internal blocking portion corresponds to a heated region that is separated from the pressure contact point between the heat roller and the pressure roller by a predetermined angle toward the upstream side in the rotation direction of the heat roller at the outer peripheral portion of the heat roller. The fixing device according to claim 1, wherein the fixing unit supports the heating unit.   The fixing device according to claim 1, wherein the internal blocking portion includes a casing that forms the gap between the outer peripheral portion and a heat insulating material filled in the casing. The housing includes a recessed portion that encloses the heating unit over a rotation axis direction of the heat roller, and a pair of arm portions that extend from both side walls of the housing to the recessed portion side,
The fixing device according to claim 3, wherein the heating unit is supported by the pair of arm units in a state of being accommodated in the recessed portion. An image forming apparatus comprising the fixing device according to claim 1.

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