JP2005283927A - Fixing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing apparatus achieving significant shortening of the warming up time in an image forming apparatus by improving efficiency of heat transmission by directly heating a fixing belt by a heater. <P>SOLUTION: In a belt type fixing apparatus 60 loaded on an image forming apparatus, a heater 62 is installed inside a cylinder of the fixing belt 61 supported on both end sides and the fixing belt 61 is directly heated by radiation heat from the heater 62. Furthermore, as a holding means for the fixing belt 61 and the heater 62, a long nip forming member 63 with an abutting surface 63a with the fixing belt 61 and a pair of belt collars 64 and 64, provided on both ends of the nip forming member 63 with the projecting of annular ribs 64b to hold the end sides of the fixing belt 61 on plate parts 64a formed with through holes to hold the end sides of the heater 62 are provided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a belt-type fixing device mounted on an image forming apparatus, and in particular, by directly heating a fixing belt with a heater, heat transfer efficiency is improved and a warm-up time of the image forming apparatus is greatly shortened. The present invention relates to a fixing device that can perform the above operation.

  Conventionally, there is an electrophotographic image forming apparatus that forms an image using toner. Such an image forming apparatus is equipped with a fixing device for fixing the transferred toner image on a sheet. There are two types of fixing devices, a two-roll type and a belt type, but the belt-type fixing device has attracted attention because of its merit that the nip width can be set wider than the two-roll type and the power consumption is low. Yes.

  As a conventional belt-type fixing device, for example, in JP-A-5-165357, an endless fixing belt 103 rotatably supported by a heat roller 101 and a support roller 102 is used as shown in FIG. In the fixing device that heats and fixes the toner image on the transfer paper when the transfer paper passes between the fixing belt 103 and the press roller 104, the position of the support roller 102 according to the type of transfer paper to be used Has been proposed to change the contact width between the fixing belt 103 and the press roller 104.

  According to such a configuration, it is possible to select an optimum nip width corresponding to paper having various thicknesses, and it is possible to select fixing conditions according to the type of transfer paper.

  In Japanese Patent Application Laid-Open No. 2003-5266, as shown in FIG. 8, the fixing roller 201, the heat roller 202, the fixing belt 203 stretched between both rollers, and the outer peripheral surface of the fixing belt 203 are contacted. In a belt fixing device including a press roller 204 for forming a nip, a position corresponding to an outlet separation portion of a nip formed by the fixing roller 201 and the press roller 204 via the fixing belt 203 and inside the fixing belt 203. A fixing device 200 having a configuration in which a fixing member 205 having a shape with a large curvature on the exit separation surface is proposed.

According to such a configuration, the separation radius is reduced to improve the separation performance, and the self-separation of the recording paper after fixing is performed without using separation means such as oil application, separation claw, separation guide plate and the like. That is, self-stripping becomes possible.
JP-A-6-165357 (Embodiments of the Invention [0019] to [0041], FIGS. 1 to 8) Japanese Patent Laid-Open No. 2003-5566 (Embodiments of the Invention [0050] to [0061], FIGS. 4 and 5)

  However, in the conventional fixing devices 100 and 200 described above, the heaters 101a and 202a are arranged inside the heat rollers 101 and 202, and the heat rollers 101 and 202 are heated by the heaters 101a and 202a. Thus, the fixing belts 103 and 203 wound around the heat rollers 101 and 202 are indirectly heated by heat conduction.

  For this reason, in the conventional fixing devices 100 and 200 described above, the heat of the heaters 101a and 202a is deprived by the heat rollers 101 and 202 in the process of heating the fixing belts 103 and 203, resulting in poor heat transfer efficiency and image quality. There was a problem that the warm-up time after the forming apparatus was turned on was long.

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a fixing device capable of improving the heat transfer efficiency by directly heating the fixing belt with a heater and greatly shortening the warm-up time of the image forming apparatus. The purpose is to provide.

  In order to achieve the above object, a fixing device according to the present invention is a belt-type fixing device mounted on an image forming apparatus, in which a heater is provided in a cylinder of a cylindrical fixing belt that holds both ends, The fixing belt is directly heated by radiant heat from the heater.

  Preferably, the holding means for the fixing belt and the heater is a long nip forming member having a contact surface with the fixing belt, attached to both ends of the nip forming member, and holds the end side of the heater. And a pair of belt collars provided with annular ribs for projecting the end side of the fixing belt.

  Preferably, the fixing belt is formed of a cylindrical Ni electroformed belt, and the inner surface of the Ni electroformed belt is painted black, or the radiant heat of the heater is reflected in the cylinder of the fixing belt. It is set as the structure which provided the mirror surface member to perform.

  More preferably, an endless press belt that is rotated by a driving unit and presses the fixing belt to follow the fixing belt, and is disposed inside the press belt, and has a contact surface with the press belt. It is set as the structure provided with the other nip formation member.

  According to the fixing device of the present invention having the above configuration, since the fixing belt can be directly heated by the heater without interposing a conventional heat roller, the heat transfer efficiency to the fixing belt is improved, The warm-up time of the image forming apparatus can be greatly shortened.

  When the nip forming member and belt collar as described above are used as the fixing belt and heater holding means, direct heating by the heater of the fixing belt can be realized with a very simple configuration.

  When the fixing belt has a configuration in which the cylindrical inner surface of the cylindrical Ni electroformed belt is painted black, the radiant heat of the heater can be efficiently absorbed by the fixing belt, and the heat transfer efficiency of the fixing belt can be further increased. As a result, the warm-up time of the image forming apparatus can be further shortened.

  When a mirror member that reflects the radiant heat of the heater is provided in the cylinder of the fixing belt, the radiant heat of the heater can be transmitted to the inner surface of the cylinder of the fixing belt without waste. The heat transfer efficiency of the belt is further improved, and the warm-up time of the image forming apparatus can be further shortened.

  When the press side that presses against the fixing belt to form a nip is a press belt, compared to a conventional press roller, the heat deprived to the press side can be greatly reduced, and the heat of the fixing belt can be reduced. The transmission efficiency is further improved, and the warm-up time of the image forming apparatus can be further shortened.

Hereinafter, a fixing device according to an embodiment of the present invention will be described. First, an image forming apparatus (printer) equipped with a fixing device according to the present embodiment will be described with reference to FIG.
FIG. 1 is a cross-sectional view illustrating the internal configuration of an image forming apparatus equipped with a fixing device according to an embodiment of the present invention. In FIG. 1, an image forming apparatus 1 is an electrophotographic tandem color image forming apparatus, and includes an image forming unit 2, an intermediate transfer belt unit 3, a paper feeding unit 4, and a duplex printing transport unit 5. It is.

  The image forming unit 2 has a configuration in which four image forming units 2M, 2C, 2Y, and 2K are arranged side by side in a multistage manner from right to left in FIG. Of these image forming units 2M, 2C, 2Y, and 2K, the three upstream image forming units 2M, 2C, and 2Y are magenta (M) and cyan (C), which are subtractive three primary colors, respectively. The monochromatic image is formed with yellow (Y) color toner, and the image forming unit 2K forms a monochrome image with black (K) toner mainly used for dark portions of characters and images.

  Each of the image forming units 2M, 2C, 2Y, and 2K has the same configuration except for the color of the toner stored in the toner container. Accordingly, the configuration of the black (K) image forming unit 2K will be described below as an example.

  The image forming unit 2K includes a photosensitive drum 21 at the bottom. The peripheral surface of the photosensitive drum 21 is made of, for example, an organic photoconductive material. A cleaner 22, a charger 23, an optical writing head 24, and a developing roller 26 of a developing unit 25 are arranged around the periphery of the photosensitive drum 21. The optical writing head 24 is separate from the image forming unit 2K. Further, the image forming unit 2K is configured to be able to be inserted and removed in the depth direction of the drawing by opening a front door (not shown) in front of the printer 1 (front side of the drawing).

  The developing unit 25 applies magenta (M), cyan (C), yellow (Y), or black (K) toner to the upper toner container as indicated by M, C, Y, and K in FIG. An intermediate portion is provided with a toner replenishing mechanism at a lower portion, a lower portion is provided with the above-described developing roller 26 at a side opening, a toner stirring member, a toner supply roller for supplying toner to the developing roller 26, a developing A doctor blade or the like for regulating the toner layer on the roller 13 to a constant layer thickness is provided.

  The intermediate transfer belt unit 3 includes a transfer belt 31 that extends in a substantially loop shape from substantially the left and right sides of the drawing at the center of the main body device, and circulates the transfer belt 31 in the counterclockwise direction of the drawing. A driving roller 32 to be moved and a driven roller 33 are provided.

  The transfer belt 31 directly transfers the toner image onto the belt surface (primary transfer) and conveys the toner image to the transfer position to the paper for further transfer (secondary transfer). The whole is called an intermediate transfer belt unit.

  The intermediate transfer belt unit 3 includes a belt position control mechanism 34 in the loop of the flat loop-shaped transfer belt 31. The belt position control mechanism 34 includes a primary transfer roller 35 made of a conductive foam sponge that presses against the lower peripheral surface of the photosensitive drum 21 via the transfer belt 31.

  The belt position control mechanism 34 includes three primary transfer rollers 35 corresponding to the three image forming units 2M, 2C, and 2Y of magenta (M), cyan (C), and yellow (Y) with a bowl-shaped support shaft. The image is transferred to the center at the same cycle, and one primary transfer roller 35 corresponding to the black (K) image forming unit 2K is rotated and moved at a rotation cycle different from the cycle of the three primary transfer rollers 35. The belt 31 is moved away from the photosensitive drum 21, and the full color mode (all four primary transfer rollers 35 are in contact with the transfer belt 31) and the monochrome mode (only the primary transfer roller 35 corresponding to the image forming unit 2K is the transfer belt). 31) and all non-transfer modes (all four primary transfer rollers 35 are separated from the transfer belt 31).

  In the intermediate transfer belt unit 3, a belt cleaner unit 36 is disposed further upstream of the uppermost image forming unit 2M in the belt moving direction on the upper surface portion, and is flat so as to be almost along the entire lower surface portion. A thin waste toner collecting container 37 is detachably disposed.

  The paper feed unit 4 includes two paper feed cassettes 41 arranged in two upper and lower stages. A paper take-out roller 42 and a paper feed are provided near the paper feed opening (right side in the drawing) of these paper feed cassettes 41, respectively. A roller 43, a separating roller 44, and a conveying roller pair 45 are arranged. In the sheet conveyance direction (vertical direction in the figure) of the conveyance roller pair 45, a secondary transfer roller 46 that is in pressure contact with the driven roller 33 via the transfer belt 31 is disposed, and a secondary transfer portion to the sheet is provided. Forming.

  A fixing device 60 according to the present embodiment is disposed downstream (upward in the drawing) of the secondary transfer portion, which will be described in detail later. Further downstream of the fixing device 60, a pair of discharge rollers 47 for discharging the fixed paper from the fixing device 60, and a pair of discharge rollers for discharging the discharged paper to a paper discharge tray 48 formed on the upper surface of the device. 49 is arranged.

  The duplex printing conveyance unit 5 includes a start return path 51a branched from the intermediate conveyance path between the carry-out roller pair 47 and the discharge roller pair 49 in the right lateral direction in the figure, an intermediate return path 51b bent downward from this, A terminal return path 51c that bends in the left lateral direction opposite to the above and finally reverses the return sheet, and three sets of return roller pairs 52a, 52b, and 52c arranged in the middle of these return paths are provided. . At the outlet of the end return path 51c, a pair of carry-in rollers 53 is disposed inside the main body.

  Next, the fixing device according to the first embodiment of the present invention mounted on the image forming apparatus will be described with reference to FIGS. FIG. 2 is a perspective view showing the fixing device according to the first embodiment of the present invention, and FIG. 3 is a perspective view showing a state where the fixing belt is removed from the fixing device of FIG. 4 is a cross-sectional view of the fixing device of FIG.

  In these drawings, the fixing device 60 of the present embodiment mainly includes a fixing belt 61, a halogen heater (heater) 62, a nip forming member 63, a pair of belt collars 64 and 64, and a press roller 65. is there.

  The fixing belt 61 has a structure in which 200 μm of silicon rubber is coated on the surface layer of a cylindrical electroformed belt having a thickness of 0.2 mm. Further, a black coating 61 a is applied to the inner surface of the fixing belt 61 so that the halogen heater 62 absorbs radiant heat well.

  The halogen heater 62 is a circular, halogen lamp that is slightly longer than the lateral width of the fixing belt 61, and is a clean, safe, small and light heat source that converts most of the input power into infrared rays (heat) and radiates it. Since the halogen heater 62 uses a filament with a small heat capacity as a heat source, radiation of heat can be started almost simultaneously with the power-on.

  The nip forming member 63 is a long plate-like body formed of a heat-resistant synthetic resin that absorbs very little heat, and holds the fixing belt 61 and the halogen heater 62 together with the belt collars 64 attached to both ends thereof. Is configured. The nip forming member 63 has a contact surface 63 a that contacts the inner surface of the fixing belt 61 when the fixing member 61 is disposed in the tube, and the corresponding contact surface 63 a is the same as the outer peripheral surface of the press roller 65. It has a concave arc surface with a radius of curvature. Such a nip forming member 63 is pressed against the press roller 65 via the fixing belt 61 to form a nip having a predetermined width.

  Each belt collar 64 is formed of a heat-resistant synthetic resin that absorbs very little heat, similar to the nip forming member 63, and is formed in a plate portion 46 a in which an insertion hole for holding the end side of the halogen heater 62 is formed. In this configuration, an annular rib 64b for projecting and holding the end side of the fixing belt 61 is provided.

  The press roller 65 is a cylindrical rubber roller urged toward the fixing belt 61 by a spring (not shown), and presses against the nip forming member 63 via the fixing belt 61 to form a nip having a predetermined width with respect to the paper P. The press roller 65 is rotationally driven by a driving means such as a motor (not shown) to drive the fixing belt 61 along the nip forming member 63 and each belt collar 64.

  According to the fixing device 60 of this embodiment having such a configuration, the fixing belt 61 is directly heated by the halogen heater 62 without interposing the conventional heat rollers 101 and 202 (see FIGS. 7 and 8). Therefore, the efficiency of heat transfer to the fixing belt 61 is improved, and the warm-up time of the image forming apparatus 1 can be greatly shortened.

  Further, by using the nip forming member 63 and the pair of belt collars 64 and 64 as the holding means for the fixing belt 61 and the heater 62, direct heating by the heater of the fixing belt is realized with a very simple configuration. can do.

  Further, the black coating 61a is applied to the inner surface of the fixing belt 61, which is a cylindrical Ni electroformed belt, so that the radiant heat of the halogen heater 62 can be efficiently absorbed by the fixing belt 61. The heat transfer efficiency of 61 is further improved, and the warm-up time of the image forming apparatus 1 can be further shortened.

  Next, a fixing device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a sectional view showing a fixing device according to the second embodiment of the present invention. Note that, in the fixing device of this embodiment, the same portions as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the fixing device 60 of the present embodiment, a mirror surface member 66 that reflects the radiant heat of the halogen heater 62 is provided on the back surface (the surface opposite to the contact surface 63 a) of the nip forming member 63 in the cylinder of the fixing belt 61. It is as. As the mirror surface member 66, for example, it is conceivable to form a convex mirror or a concave mirror on the back surface of the nip forming member 63 with a metal excellent in light / heat reflection such as aluminum foil or silver plating.

  According to such a configuration, by reflecting the radiant heat of the halogen heater 62 to the mirror member 66, the radiant heat can be transmitted to the cylinder inner surface of the fixing belt 61 without waste, and the black coating 61a on the cylinder inner surface is provided. In combination with this, the heat transfer efficiency of the fixing belt 61 is further improved, and the warm-up time of the image forming apparatus 1 can be further shortened.

  Next, a fixing device according to a third embodiment of the present invention will be described with reference to FIG. FIG. 6 is a sectional view showing a fixing device according to a third embodiment of the present invention. Note that, in the fixing device of this embodiment, the same portions as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  The fixing device 60 of the present embodiment is configured to employ a press belt 71 instead of the press roller 65 in the first and second embodiments. The press belt 71 is an endless belt having substantially the same width as the lateral width of the fixing belt 61, and engaging portions 71a for driving force transmission similar to the timing belt are projected from both ends of the back surface by integral molding. . As a material of such a press belt 71, polyimide excellent in heat insulation, heat resistance, slidability, high strength, high toughness and the like is preferable.

  Further, inside the press belt 71, a nip forming member 72 is disposed at the upper portion, and a pair of belt pulleys 73, 73 are disposed opposite to the front and rear of the lower portion, respectively. It has a substantially triangular shape with 72 as a vertex.

  The nip forming member 72 has a convex arcuate contact surface 72 a having the same radius of curvature as the contact surface 63 a of the nip forming member 63 disposed in the fixing belt 61. A nip having a predetermined width with respect to the paper P is formed by being pressed against the forming member 63.

  Each belt pulley 73 is formed with a meshing portion 73 a corresponding to the meshing portion 71 a of the press belt 71, and transmits the driving force of a driving means (not shown) to bring the press belt 71 into contact with the nip forming member 72. It is driven to rotate while sliding on the surface 72a. Further, only the belt pulley 73 disposed on the paper discharge side (see the arrow in the figure) of the paper P is biased toward the paper discharge side, so that the press belt 71 is not bent.

  According to such a configuration, the press roller 65 (see FIGS. 4 and 5) according to the first and second embodiments is formed by using the thin press belt 71 on the press side that forms a nip by pressing against the fixing belt 61. ) Can be greatly reduced, the heat transfer efficiency of the fixing belt 61 can be further improved, and the warm-up time of the image forming apparatus 1 can be further shortened. .

  The fixing device of the present invention is not limited to the above-described first to third embodiments. For example, the fixing means of the fixing belt 61 is not limited to the nip forming member 63 and the pair of belt collars 64 and 64 described above, and can hold the fixing belt 61 rotatably, As long as the halogen heater 62 can be held and a nip formation with the press side is possible, the configuration may be changed to another configuration.

1 is a cross-sectional view illustrating an internal configuration of an image forming apparatus equipped with a fixing device according to an embodiment of the present invention. 1 is a perspective view showing a fixing device according to a first embodiment of the present invention. FIG. 3 is a perspective view showing a state where a fixing belt is removed from the fixing device of FIG. 2. FIG. 3 is a cross-sectional view of the fixing device in FIG. 2. FIG. 6 is a cross-sectional view illustrating a fixing device according to a second embodiment of the present invention. FIG. 6 is a cross-sectional view illustrating a fixing device according to a third embodiment of the present invention. FIG. 10 is a cross-sectional view showing a fixing device according to a conventional example. It is sectional drawing which shows the fixing device which concerns on another prior art example.

Explanation of symbols

1 Image forming device (printer)
2 Image forming unit 2M, 2C, 2Y, 2K Image forming unit 21 Photosensitive drum 22 Cleaner 23 Charger 24 Optical writing head 25 Developer 26 Developing roller 3 Intermediate transfer belt unit 31 Transfer belt 32 Drive roller 33 Driven roller 34 Belt Position control mechanism 35 Primary transfer roller 36 Belt cleaner unit 37 Waste toner collection container 4 Paper feed unit 41 Paper feed cassette 42 Paper take-out roller 43 Feed roller 44 Rolling roller 45 Conveying roller pair 46 Secondary transfer roller 47 Unloading roller pair 48 Ejection Paper tray 49 Paper discharge roller pair 5 Duplex printing transport unit 51a Start return path 51b Intermediate return path 51c End return path 52a, 52b, 52c Return roller pair 53 Carry-in roller pair 60 Fixing device 61 Fixing belt (Ni electroforming belt)
61a Black paint 62 Halogen heater (heater)
63 Nip forming member 63a Contact surface 64 Belt collar 64a Plate portion 64b Annular rib 65 Press roller 66 Mirror surface member 71 Press belt 72 Nip forming member 72a Contact surface 73 Belt pulley 73a Engagement portion

Claims (5)

  In a belt-type fixing device mounted in an image forming apparatus, a heater is disposed in a cylinder of a cylindrical fixing belt that holds both ends, and the fixing belt is directly heated by radiant heat from the heater. A fixing device characterized.   As a holding means for the fixing belt and the heater, a long nip forming member having a contact surface with the fixing belt, and an insertion for holding the end side of the heater attached to both ends of the nip forming member The fixing device according to claim 1, further comprising: a pair of belt collars provided with annular ribs for projecting an end of the fixing belt on the plate portion in which the holes are formed.   3. The fixing device according to claim 1, wherein the fixing belt is formed of a cylindrical Ni electroformed belt and the inner surface of the Ni electroformed belt is painted black.   4. The fixing device according to claim 1, wherein a mirror member that reflects the radiant heat of the heater is provided in a cylinder of the fixing belt.   An endless press belt that is rotated by a driving means and presses the fixing belt to follow the fixing belt, and another nip formed inside the press belt and having a contact surface with the press belt The fixing device according to claim 1, further comprising a member.

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