JP6512138B2 - Fixing device and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device for fixing a toner image on a sheet, and an image forming apparatus provided with the fixing device.

  An electrophotographic image forming apparatus such as a copying machine, a printer, a fax machine, and a multifunction machine includes a fixing device for fixing a toner image on a sheet. In a fixing device of a full color image forming apparatus, an endless fixing belt heated by a heat source, a fixing roller rotatably provided inside the fixing belt, and a pressure roller pressed against the fixing roller through the fixing belt , And forms a fixing nip between the fixing belt and the pressure roller.

  The fixing roller has a cored bar made of aluminum, iron or the like, and an elastic layer provided on the outer peripheral surface of the cored bar. The elastic layer is formed of a material having a low thermal conductivity, such as silicone rubber or a foam material, to suppress heat transfer from the fixing belt. The fixing belt has an elastic layer and a releasing layer sequentially formed on the surface of a base layer formed of nickel or the like, and the fixing belt is generated by the base layer generating heat due to a heating source such as IH. Is heated.

  In such a fixing device, since a slight clearance is opened between the fixing roller and the fixing belt, the fixing belt may meander depending on the contact state between the fixing belt and the sheet. Therefore, Patent Document 1 describes a fixing device in which anti-slip members are provided outside the both end surfaces of the fixing belt at predetermined intervals in consideration of thermal expansion and dimensional tolerance of the fixing belt. In this fixing device, when the fixing belt meanders, the end face is in contact with either one of the anti-slip members, so that the meandering is restricted.

  On the other hand, the fixing belt may be charged by contact with the sheet. Therefore, in some cases, the anti-slip member is formed of metal or conductive resin, and the charge of the fixing belt is removed from the anti-slip member through the core metal.

JP, 2010-169737, A

  However, in the fixing device described in Patent Document 1, the fixing belt is in an electrically floating state until the fixing belt meanders and abuts on one of the detent members. In addition, the elastic layer of the fixing roller thermally expands when heated by the fixing belt and contacts the fixing belt, and the fixing belt may not be able to move in the axial direction due to the friction between the elastic layer and the fixing belt. If the fixing belt can not move in the axial direction before the fixing belt abuts on one of the anti-slip members, the fixing belt is maintained in an electrically floating state. As described above, when the fixing belt continues to be charged, noise may be generated by the discharge to affect the electric components such as the thermistor.

  An object of the present invention is to provide a fixing device and an image forming apparatus capable of reliably discharging the fixing belt in consideration of the above circumstances.

  In order to solve the above problems, a fixing device according to the present invention includes: an endless fixing belt heated by a heat source; a fixing roller provided inside the fixing belt so as to be rotatable about a rotation axis; A pressure member rotating in pressure contact with the fixing roller via the fixing roller, and forming a fixing nip between the fixing belt and the pressure member, the fixing device comprising: It is provided with a conductive detent member disposed opposite to the end face on the outer side in the rotational axis direction and grounded, and a diselectrifying member provided on the detent member and always in contact with the fixing belt. It is characterized by

  By adopting such a configuration, the fixing belt is always grounded via the charge removing member and the anti-slip member, so the electrified charge of the fixing belt is rapidly eliminated via the anti-slip member, and the fixing belt is charged. Can prevent discharge from the

  In the fixing device of the present invention, the fixing belt includes a conductive layer and an elastic layer provided outside the conductive layer, and the charge removing member is in contact with the conductive layer of the fixing belt. It may be characterized by

  By employing such a configuration, the fixing belt can be destaticized more efficiently.

  In the fixing device of the present invention, the charge removing member may be in contact with the fixing belt on the outer side in the rotational axis direction than the fixing nip.

  By adopting such a configuration, even if the detent member rotates and the charge removal member reaches the fixing nip, the charge removal member is not sandwiched between the fixing belt and the pressure member, so the rotation of the shift detent member It is possible to prevent the damage of the charge removal member or the

  In the fixing device according to the present invention, the charge removing member may have a conductive brush and a conductive holder which is placed on the conductive brush and supported by the shift stopper. .

  By adopting such a configuration, the static elimination member can easily follow the meandering or deformation of the fixing belt, so that the static elimination member can be more reliably in contact with the fixing belt.

  An image forming apparatus according to the present invention includes any one of the above-described fixing devices.

  According to the present invention, since the charge removing member is in contact with the fixing belt, the fixing belt can be reliably removed of charge via the charge removing member and the anti-slip member.

FIG. 1 is a schematic view showing an outline of a color printer according to an embodiment of the present invention. FIG. 1 is a front cross-sectional view of a fixing device according to an embodiment of the present invention. FIG. 6 is a side cross-sectional view showing the fixing belt during normal traveling in the fixing device according to the embodiment of the present invention. FIG. 5 is a side sectional view showing the fixing belt at the time of meandering travel in the fixing device according to the embodiment of the present invention. FIG. 6 is a side sectional view showing the fixing belt in which the discharging brush is passing through the fixing nip in the fixing device according to the embodiment of the present invention. FIG. 6A is a front view, and FIG. 6B is a side view of the static elimination member in the fixing device according to the embodiment of the present invention.

  Hereinafter, a fixing device and an image forming apparatus according to an embodiment of the present invention will be described with reference to the attached drawings.

  First, the entire configuration of a color printer 1 as an image forming apparatus will be described with reference to FIG. FIG. 1 is a schematic view showing an outline of a color printer. In the following description, the front-rear direction shown in FIG. 1 is referred to as the front-rear direction of the color printer 1, and the left-right direction is based on the direction when the color printer 1 is viewed from the front side.

  As shown in FIG. 1, the color printer 1 includes a box-shaped case 2. A sheet discharge outlet 4 and a sheet discharge tray 5 provided below the sheet discharge outlet 4 are formed on the top surface of the housing 2. A rear opening 2 a is formed on the rear side surface of the housing 2. The rear opening 2a is opened and closed by a rear cover 6 rotatably supported about a lower end. Furthermore, inside the rear opening 2a, the transport unit 7 is supported rotatably around the lower end.

  In the lower part of the housing 2, the sheet feeding cassette 9 in which the sheet S is accommodated is detachably accommodated, and at the upper right of the sheet feeding cassette 9, the sheet feeding device 10 that feeds the sheet S from the sheet feeding cassette 9 is It is provided. Further, an exposure device 12 is provided above the sheet feeding cassette 9. Above the exposure device 12, an intermediate transfer unit 14 and four image forming units 15 arranged below the intermediate transfer unit 14 in the front-rear direction are provided. The intermediate transfer unit 14 has an intermediate transfer belt 17 rotatably supported, and four primary transfer rollers 18 arranged in line in the front-rear direction inside the intermediate transfer belt 17.

  The four image forming units 15 include a photosensitive drum 20 rotatably provided, a charger 21 disposed along the rotational direction of the photosensitive drum 20 around the photosensitive drum 20, and a developing device 22. The cleaning device 23 and the charge removal device 24 are provided. The photosensitive drum 20 faces the primary transfer roller 18 between the developing device 22 and the cleaning device 23 via the intermediate transfer belt 17, and a primary transfer portion between the intermediate transfer belt 17 and the photosensitive drum 20. 26 form. Each image forming unit 15 is connected to a toner container (not shown) in which toner of the corresponding color is stored, and the toner is supplied to the developing device 22 from the toner container.

  Behind the intermediate transfer unit 14, a secondary transfer roller 28 is rotatably supported by the transport unit 7, and a secondary transfer portion 29 is formed between the intermediate transfer belt 17 and the secondary transfer roller 28. There is. A fixing device 30 is provided above the secondary transfer unit 29, and a paper discharge device 31 facing the paper discharge port 4 is provided above the fixing device 30.

  Further, inside the housing 2, a main conveyance path 33 of the sheet S and a double-sided printing path 34 are formed. The main conveyance path 33 is formed inside the conveyance unit 7 so as to go from the sheet feeding device 10 to the discharge device 31 through the secondary transfer portion 29 and the fixing device 30. The duplex printing path 34 branches from the downstream side of the fixing device 30 in the transport direction of the main transport path 33 and merges with the main transport path 33 at the downstream side of the sheet feeding device 10. It is formed between.

  Next, an image forming operation of the color printer 1 having such a configuration will be described. First, in each image forming unit 15, after the surface of the photosensitive drum 20 is charged by the charger 21, the photosensitive drum 20 is exposed by the laser light from the exposure device 12 in accordance with the image data. An electrostatic latent image is formed on the surface of the photosensitive drum 20. The electrostatic latent image is developed into a toner image by the developing device 22, and the toner image is transferred to the intermediate transfer belt 17 at the primary transfer portion 26. The toner and charge remaining on the photosensitive drum 20 are removed by the cleaning device 23 and the charge removing device 24, respectively. The toner images formed by the respective image forming units 15 are superimposed on the intermediate transfer belt 17 to form a full color toner image on the intermediate transfer belt 17.

  On the other hand, the sheet S fed from the sheet feeding cassette 9 by the sheet feeding device 10 is conveyed along the main conveyance path 33 to the secondary transfer portion 29 at the same timing as the toner image forming operation described above. In the section 29, the toner image on the intermediate transfer belt 17 is secondarily transferred onto the sheet S. The sheet S on which the toner image has been secondarily transferred is conveyed to the downstream side of the main conveyance path 33 to enter the fixing device 30, and the toner image is fixed on the sheet S in the fixing device 30. The sheet S on which the toner image is fixed is discharged from the discharge device 31 to the discharge tray 5. When duplex printing is performed, the sheet S on which an image is formed on one side is branched from the main transport path 33 to the duplex printing path 34, transported through the duplex printing path 34, and merged into the main transport path 33. Similarly, image formation is performed on the other side.

  Next, the fixing device 30 will be described with reference to FIGS. 2 is a front sectional view showing the fixing device, FIG. 3 to FIG. 6 are side sectional views showing the fixing device, FIG. 3 is a fixing belt normal traveling, FIG. 4 is a fixing belt meandering traveling, FIG. Shows that the fixing roller has rotated until it reaches the fixing nip. FIG. 6 is a view showing the charge removing member, FIG. 6 (A) is a front view, and FIG. 6 (B) is a side view.

  As shown in FIGS. 2 and 3, the fixing device 30 includes a fixing belt 41, an IH heater 42 as a heating source for heating the fixing belt 41, and a fixing roller 43 rotatably provided inside the fixing belt 41. The pressure roller 44, which is a pressure member that rotates in pressure contact with the fixing roller 43 via the fixing belt 41, the anti-slip members 45 provided on the outside of both end surfaces of the fixing belt 41, and the anti-slip members 45 And a charge removing member 46 provided on the

  The fixing belt 41 is an endless belt having a predetermined inner diameter and a width longer than a sheet passing area through which a sheet is passed, and a base layer formed of a magnetic metal such as nickel, silicone rubber, etc. And a release layer such as a PFA tube are laminated in order from the inner side.

  The IH heater 42 has a coil portion 42a, a coil bobbin 42b that holds the coil portion 42a in a wound shape, and an arch core 42c. The IH heater 42 is supported so as to cover the upper half of the fixing belt 41. A magnetic field is generated by applying a high frequency AC voltage to the coil portion 42a, and an eddy current is generated in the base material layer of the fixing belt 41 by the action of the magnetic field, and the base material layer generates heat to heat the fixing belt 41. Ru.

  The fixing roller 43 has a cored bar 51 as a rotating shaft, and an elastic layer 52 provided on the outer peripheral surface of the cored bar 51. The cored bar 51 has a central portion 51 a and outer ends 51 b provided on both outer sides of the central portion 51 a and smaller in diameter than the central portion 51 a. The length of the central portion 51 a is shorter than the width of the fixing belt 41. Further, in both outer end portions 51b, an annular groove 51c is formed along the outer peripheral surface near the center in the axial direction. The cored bar 51 is formed of aluminum, iron or the like.

  The elastic layer 52 is provided around the central portion 51 a of the core metal 51 and has an outer diameter smaller than the inner diameter of the fixing belt 41. Further, on both end surfaces of the elastic layer 52, stepped portions 52a cut out along the outer periphery are formed. The elastic layer 52 is formed of a material having a low heat transfer coefficient, such as silicone rubber or a foamed resin.

  The fixing roller 43 is inserted inside the fixing belt 41, and the ends of the outer ends 51b of the core metal 51 are supported by the bearings 56 via the conductive bushes 55, respectively. The bearing 56 is supported by a conductive frame (not shown) of the housing 2. Thereby, the core metal 51 is grounded to the housing 2 through the bush 55 and the bearing 56. Further, a slight clearance is interposed between the fixing belt 41 and the fixing roller 43.

  The pressure roller 44 has a cylindrical core metal 44a, an elastic layer 44b provided on the outer peripheral surface of the core metal 44a, and a release layer (not shown) provided on the outer peripheral surface of the elastic layer 44b. There is. The pressure roller 44 is supported so as to be in pressure contact with the fixing roller 43 from below the fixing roller 43 via the fixing belt 41 to form the fixing nip 58, and is connected to a drive source (not shown) to be rotationally driven. Be done. When the pressure roller 44 is rotated in the counterclockwise direction in FIG. 2 by the driving source, the fixing belt 41 and the fixing roller 43 are driven to rotate in the clockwise direction opposite to the rotation direction of the pressure roller 44. Thus, the sheet having passed through the fixing nip 58 is conveyed.

  When the pressure roller 44 is in pressure contact with the fixing roller 43, as shown in FIG. 3, the elastic layer 52 of the fixing roller 43 is pressed and deformed. Along with this deformation, both end portions of the fixing belt 41 are deformed so as to bend inward in the step portion 52 a of the elastic layer 52.

  The anti-slip member 45 has a cylindrical main body portion 71 and a collar portion 72 projecting radially from one end of the main body portion 71. The main body portion 71 has an inner diameter slightly larger than the outer diameter of the outer end portion 51 b of the cored bar 51 of the fixing roller 41. The collar portion 72 has an outer diameter larger than the outer diameter of the fixing belt 41. The collar portion 72 is formed with a slit 73 along the tangential direction of the main body portion 71.

  The static elimination member 46 has the electroconductive brush 77 and the electroconductive holder 78 by which the brush 77 is installed, as FIG. 6 shows. The brush 77 is formed of conductive brush hair containing stainless steel or carbon. The holder 78 has a flat rectangular parallelepiped shape, and a brush bundle formed by bundling a plurality of brush bristles is implanted on one side surface at a predetermined interval in parallel. The support portion 78a on which the brush 77 is implanted is bent at an obtuse angle. The holder 78 is formed of a conductive material such as aluminum.

  The holder 78 is fixed to the main body 71 through the slits 73 formed in the collar 72 of the anti-slip member 45, and the brush 77 is inclined radially outward from the main body 71.

  The main body 71 of the anti-slip member 45 supporting the static elimination member 46 is rotatably fitted to the outer end 51 b of the core metal 51 of the fixing roller 43, and the collar 72 is fixed to the fixing belt 41. The end face of the is opposed with a predetermined gap. Further, the slide ring 81 engaged with the annular groove 51 c of each outer end 51 b restricts the sliding of the anti-slip member 45 in the axial outward direction. Further, by being supported by the core metal 51 in this manner, the anti-slip member 45 is grounded to the conductive frame of the housing 2 via the core metal 51.

  The free end of the brush 77 protrudes outward beyond the fixing belt 41, but enters the step 52a of the elastic layer 52 of the fixing roller 43, and the brush bristles move the inner surface of the fixing belt 41, that is, the brush. , In contact with the base layer.

  Furthermore, while the fixing belt 41 moves in the axial direction between the two offset members 45, the brush 77 can always contact the fixing belt 41 while the outer peripheral edge of the end face of the elastic layer 52 of the fixing roller 43 (step The length is set so as not to reach the outer peripheral edge of the portion 52a.

  Further, as shown in FIG. 2, fixing device 30 is provided with sheet entry guide 63 provided upstream of fixing nip 58 in the sheet conveyance direction, and separation member 64 provided downstream of fixing nip 58 in the sheet conveyance direction. And a thermistor 65 for detecting the temperature of the fixing belt 41. The paper entry guide 63 is disposed along the main conveyance path 33 so as to incline upward toward the fixing nip 58. The separation member 64 is supported so as to face the surface of the fixing belt 41 from the counter direction with respect to the rotation direction of the fixing belt 41. The thermistor 65 is supported on the fixing belt 41 in a noncontact manner.

  In the fixing device 30 having the above configuration, the sheet S to which the toner image has been transferred is guided by the sheet entry guide 63 and conveyed to the fixing nip 58. When the sheet S passes through the fixing nip 58, the sheet S is heated by the fixing belt 41 and pressurized by the pressure roller 44 and the fixing roller 43, and the toner image is fixed to the sheet S. The leading end of the sheet S on which the toner is fixed is separated from the fixing belt by the separating member 64, and is conveyed along the main conveyance path 33. Further, the IH heater 42 is controlled based on the temperature of the fixing belt 41 detected by the thermistor 65.

  Then, as shown in FIG. 3, the charge removing member 46 supported by the anti-slip member 45 is in contact with the inner surface (base material layer) of the fixing belt 41. That is, the fixing belt 41 is grounded to the conductive frame of the housing 2 via the charge removing member 46, the anti-slip member 45, the core metal 51, the bush 55, and the bearing 56. Therefore, even if the sheet S passing through the fixing nip 58 and the fixing belt 41 may be charged due to friction, the electrostatic charge is determined by the charge removing member 46, the anti-slip member 45, the core metal 51, the bush 55, and the bearing. It is quickly discharged through 56.

  Further, as shown in FIG. 4, when the fixing belt 41 meanders in one direction (left direction in the drawing), the end face of the fixing belt 41 abuts against the anti-slip member 45, and the meandering of the fixing belt 41 is restricted. Be done. The tip of the brush 77 of the static elimination member 46 enters the step 52 a of the elastic layer 52 of the fixing roller 43 and has a length capable of coming into contact with the fixing belt 41. The brush 77 also abuts on the part. Therefore, even when the fixing belt 41 meanders, the static elimination member 46 can be reliably brought into contact with the fixing belt 41.

  Further, when the fixing roller 43 rotates, the anti-slip member 45 also rotates following the rotation. As shown in FIG. 5, even if the detent member 45 rotates and the static elimination member 46 reaches the fixing nip 58, the brush 77 is an outer peripheral edge of the end face of the elastic layer 52 of the fixing roller 43 (outside of the step 52 a Therefore, the toner does not get caught between the fixing belt 41 and the pressure roller 44 at the fixing nip 58.

  As described above, in the fixing device 30 of the present invention, since the charge removing member 46 is always in contact with the inner surface of the fixing belt 41, even if the fixing belt 41 is charged due to friction with the sheet, the charge removing member 46 is Thus, the fixing belt 41 can be prevented from being charged. Therefore, the generation of noise and the like due to the discharge of the fixing belt 41 charged can be prevented.

  Further, since the charge removing member 46 is brought into contact with the inner surface of the fixing belt 41, the fixing belt 41 can be reliably removed. As described above, the fixing belt 41 has a three-layer structure having a base material layer, an elastic layer, and a releasing layer. Such a fixing belt 41 is formed, for example, by preparing a sheet material having a three-layer structure, cutting the sheet material into a predetermined length, and winding the cut sheet material endlessly. Here, when the sheet material is cut by the cutting blade from the release layer side, in the cut surface, the release layer wraps around the elastic layer side in the cutting direction tip side, and the elastic layer is further cut in the cutting direction It may wrap around to the side substrate layer. As a result, the conductive base layer is less likely to be exposed from the cut surface. That is, the base material layer is less likely to be exposed at the end face of the fixing belt 41.

  Therefore, for example, when the detent member for static elimination is brought into contact with the end face of the fixing belt 41, there is a possibility that the base layer of the detent member does not sufficiently contact the detent member, and efficient decharging can not be performed. is there.

  Therefore, the charge removing member 6 can be brought into direct contact with the inside of the fixing belt 41, that is, the base material layer, so that the charge can be efficiently removed.

  Further, since the charge-removing member 46 has a brush-like flexible shape, it can follow the meandering and deformation of the fixing belt 41, and can be reliably brought into contact with the fixing belt 41. Furthermore, due to the elasticity of the brush bristles, the base material layer of the fixing belt 41 can be stably brought into contact. Note that a conductive member having elasticity such as a sponge shape or a plate spring shape can also be used as the charge removal member 46.

  In addition, since the brush 77 is not pinched between the fixing belt 41 and the pressure roller 44 at the fixing nip 58 during rotation of the anti-slip member 45, rotation of the anti-slip member 45 is inhibited or the charge removing member 46 There is no damage.

  In the embodiment of the present invention, the case where the configuration of the present invention is applied to the color printer 1 has been described, but in another different embodiment, the present invention is applied to an image forming apparatus other than the color printer 1 such as a copying machine, a facsimile, or a multifunction machine. The configuration of the invention may be applied.

  Furthermore, since the description of the embodiments of the present invention described above describes the preferred embodiments of the fixing device and the image forming apparatus according to the present invention, even when technically preferable limitations are given. However, the technical scope of the present invention is not limited to these embodiments unless specifically described to limit the present invention. That is, the components in the embodiment of the present invention described above can be appropriately replaced with existing components and the like, and various variations are possible including combinations with other existing components, The description of the embodiments of the present invention described above does not limit the contents of the invention described in the claims.

1 Color printer (image forming device)
Reference Signs List 30 fixing device 41 fixing belt 43 fixing roller 44 pressure roller (pressure member)
45 anti-slip member 46 static elimination member 58 fixing nip 77 brush 78 holder

Claims (6)

An endless fixing belt heated by a heat source, a fixing roller rotatably provided on the inner side of the fixing belt around a rotation axis, and pressure applied to the fixing roller by pressure via the fixing belt. A fixing device that includes a member and forms a fixing nip between the fixing belt and the pressing member,
In the axial direction outside of the rotation axis of the end surface of the fixing belt is disposed to face the end surface fitted rotatably to the rotating shaft, the deviation check of conductive and is grounded via the rotary shaft Members,
A fixing device comprising: a static elimination member provided on the slip prevention member and always in contact with the fixing belt. The fixing belt has a conductive layer and an elastic layer provided on the outer side of the conductive layer,
The fixing device according to claim 1, wherein the charge removing member is in contact with the conductive layer of the fixing belt. The charge eliminating member, fixing device according to claim 1 or 2, characterized in that in contact with the fixing belt in front Symbol axially outer than the fixing nip.   The said static elimination member has an electroconductive brush, The electroconductive holder by which this brush is planted and supported by the said offset member, The electroconductive member characterized by the above-mentioned. The fixing device according to item 1.   The slip stopper is
  The holder has a cylindrical main body portion supported by the holder of the static elimination member and fitted to the rotary shaft, and a flange portion radially projecting from one end of the main body portion and facing the end surface;
  The holder of the charge removal member has a support portion bent in the axial direction,
  The fixing device according to claim 4, wherein the brush is embedded in the support portion and is in contact with an inner peripheral surface of the fixing belt in a posture inclined with respect to the rotation axis. An image forming apparatus comprising the fixing device according to any one of claims 1 to 5 .

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