JP2017156612A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device that can reliably eliminate static electricity on a fixing belt.SOLUTION: A fixing device 30 comprises: an endless fixing belt 41 that is heated by a heat source; a fixing roller 43 that is rotatably provided on a rotation shaft on the inside of the fixing belt 41; and a pressure member 44 that rotates in pressure contact with the fixing roller 43 with the fixing belt 41 therebetween, and the fixing device forms a fixing nip 58 between the fixing belt 41 and pressure member 44. The fixing device 30 includes: conductive skew prevention members 45 that are arranged to face the end faces of the fixing belt 41 on the outside in the direction of rotation shaft of the end faces and are grounded; and static elimination members 46 that are provided on the skew prevention members 45 and in constant contact with the fixing belt 41.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a fixing device that fixes a toner image on a sheet, and an image forming apparatus including the fixing device.

  2. Description of the Related Art An electrophotographic image forming apparatus such as a copying machine, a printer, a fax machine, and a multifunction machine includes a fixing device that fixes 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, a pressure roller pressed against the fixing roller via the fixing belt, And a fixing nip is formed between the fixing belt and the pressure roller.

  The fixing roller has a metal core formed of aluminum, iron, or the like, and an elastic layer provided on the outer peripheral surface of the metal core. The elastic layer is formed of a material having low thermal conductivity such as silicone rubber or foamed material, and suppresses heat transfer from the fixing belt. The fixing belt has an elastic layer and a release layer formed in order on the surface of the base material layer formed of nickel or the like, and the fixing belt generates heat when the base material layer generates heat by a heating source such as IH. Is heated.

  In such a fixing device, since a slight clearance is provided between the fixing roller and the fixing belt, the fixing belt may meander depending on the contact state between the fixing belt and the paper. Therefore, Patent Document 1 describes a fixing device in which a detent member is provided outside the both end faces of the fixing belt with a predetermined interval in consideration of thermal expansion and dimensional tolerance of the fixing belt. In this fixing device, when the fixing belt meanders, the end face comes into contact with one of the detent members and the meandering is regulated.

  On the other hand, the fixing belt may be charged by contact with paper. Therefore, there is a case where the stopper member is formed of a metal or a conductive resin, and the charge of the fixing belt is discharged from the stopper 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 comes into contact with one of the detent members. Further, when the elastic layer of the fixing roller is heated by the fixing belt, the elastic layer expands and contacts the fixing belt, and the fixing belt may not be able to move in the axial direction due to friction between the elastic layer and the fixing belt. If the fixing belt cannot move in the axial direction before the fixing belt comes into contact with one of the detent members, the fixing belt is maintained in an electrically floating state. If the fixing belt continues to be charged in this way, noise may be generated by discharge, which may affect electrical components such as the thermistor.

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a fixing device and an image forming apparatus that can reliably remove static electricity from a fixing belt.

  In order to solve the above problems, the fixing device of 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, and the fixing belt. A pressure member that rotates in pressure contact with the fixing roller, and forms a fixing nip between the fixing belt and the pressure member. A conductive detent member disposed opposite to the end surface on the outer side in the rotational axis direction and grounded, and a static elimination member provided on the detent member and constantly contacting the fixing belt. It is characterized by that.

  By adopting such a configuration, since the fixing belt is always grounded via the static eliminating member and the detent member, the charged charge of the fixing belt is quickly eliminated through the detent member and charged. Can be prevented from discharging.

  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 eliminating member is in contact with the conductive layer of the fixing belt. It may be characterized.

  By adopting such a configuration, the fixing belt can be discharged more efficiently.

  In the fixing device according to the aspect of the invention, the charge eliminating member may be in contact with the fixing belt on the outer side in the rotation axis direction than the fixing nip.

  By adopting such a configuration, even if the anti-static member rotates and the static eliminating member reaches the fixing nip, the static eliminating member is not sandwiched between the fixing belt and the pressure member. Can be prevented, and the static elimination member can be prevented from being damaged.

  In the fixing device of the present invention, the charge removal member may include a conductive brush and a conductive holder in which the conductive brush is implanted and supported by the detent member. .

  By adopting such a configuration, the static elimination member can easily follow the meandering and deformation of the fixing belt, and thus the static elimination member can be brought into contact with the fixing belt more reliably.

  The image forming apparatus of the present invention includes any one of the fixing devices described above.

  According to the present invention, since the static elimination member contacts the fixing belt, the static electricity can be reliably eliminated from the fixing belt via the static elimination member and the detent member.

1 is a schematic diagram illustrating an outline of a color printer according to an embodiment of the present invention. 1 is a front sectional view of a fixing device according to an embodiment of the present invention. FIG. 3 is a side sectional view showing the fixing belt during normal running in the fixing device according to the embodiment of the present invention. In the fixing device according to an embodiment of the present invention, FIG. In the fixing device according to an embodiment of the present invention, a side cross-sectional view showing a fixing belt while a static elimination brush is passing through a fixing nip. FIGS. 6A and 6B are diagrams illustrating a static elimination member in a fixing device according to an embodiment of the present invention, in which FIG. 6A is a front view and FIG. 6B is a side view.

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

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

  As shown in FIG. 1, the color printer 1 includes a box-shaped housing 2. A paper discharge port 4 and a paper discharge tray 5 provided below the paper discharge port 4 are formed on the upper 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 supported so as to be rotatable about the lower end. Further, a transport unit 7 is supported inside the rear opening 2a so as to be rotatable about the lower end.

  A paper feeding cassette 9 that contains paper S is detachably housed in the lower part of the housing 2, and a paper feeding device 10 that feeds the paper S from the paper feeding cassette 9 is located at the upper right of the paper feeding cassette 9. Is provided. An exposure device 12 is provided above the paper feed 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 includes an intermediate transfer belt 17 that is rotatably supported, and four primary transfer rollers 18 that are arranged inside the intermediate transfer belt 17 in the front-rear direction.

  The four image forming units 15 include a photosensitive drum 20 that is rotatably provided, a charger 21 that is disposed around the photosensitive drum 20 along the rotation direction of the photosensitive drum 20, a developing device 22, Each has a cleaning device 23 and a charge removal device 24. The photosensitive drum 20 is opposed to the primary transfer roller 18 via the intermediate transfer belt 17 between the developing device 22 and the cleaning device 23, and the primary transfer unit is interposed between the intermediate transfer belt 17 and the photosensitive drum 20. 26 is formed. Each image forming unit 15 is connected to a toner container (not shown) that stores toner of a corresponding color, and the toner is supplied from the toner container to the developing device 22.

  A secondary transfer roller 28 is rotatably supported by the transport unit 7 behind the intermediate transfer unit 14, and a secondary transfer portion 29 is formed between the intermediate transfer belt 17 and the secondary transfer roller 28. Yes. 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, a main transport path 33 and a double-sided printing path 34 for the paper S are formed inside the housing 2. 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 unit 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 joins the main transport path 33 on the downstream side of the sheet feeding device 10. 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, exposure corresponding to the image data is performed on the photosensitive drum 20 by the laser light from the exposure device 12. 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 by the primary transfer unit 26. The toner and charge remaining on the photosensitive drum 20 are removed by the cleaning device 23 and the charge eliminating device 24, respectively. The toner images formed by the image forming units 15 are superimposed on the intermediate transfer belt 17, so that a full-color toner image is formed 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 transported to the secondary transfer unit 29 along the main transport path 33 in synchronism with the toner image forming operation described above, and is subjected to secondary transfer. The toner image on the intermediate transfer belt 17 is secondarily transferred to the paper S in the portion 29. The sheet S on which the toner image is secondarily transferred is conveyed downstream through the main conveyance path 33 and enters the fixing device 30, and the toner image is fixed on the sheet S in the fixing device 30. The paper S on which the toner image is fixed is discharged from the paper discharge device 31 to the paper discharge tray 5. When duplex printing is performed, the sheet S on which an image is formed on one side branches from the main conveyance path 33 to the duplex printing path 34, is conveyed through the duplex printing path 34, and joins the main conveyance path 33. Thus, image formation is similarly performed on the other surface.

  Next, the fixing device 30 will be described with reference to FIGS. 2 is a front sectional view showing the fixing device, FIGS. 3 to 6 are side sectional views showing the fixing device, FIG. 3 is when the fixing belt is normally running, FIG. 4 is when the fixing belt is meandering, and FIG. Shows a state in which the fixing roller rotates until reaches the fixing nip. 6A and 6B are diagrams showing the charge removal member. FIG. 6A is a front view and FIG. 6B is a side view.

  As shown in FIG. 2 and FIG. 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 that is rotatably provided inside the fixing belt 41. A pressure roller 44 that is a pressure member that rotates in pressure contact with the fixing roller 43 via the fixing belt 41, a locking member 45 provided outside both end surfaces of the fixing belt 41, and each locking member 45. The static elimination member 46 provided in the.

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

  The IH heater 42 includes a coil portion 42a, a coil bobbin 42b that holds the coil portion 42a in a winding 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. Due to the action of this magnetic field, an eddy current is generated in the base material layer of the fixing belt 41, the base material layer generates heat, and the fixing belt 41 is heated. The

  The fixing roller 43 includes a cored bar 51 as a rotation shaft and an elastic layer 52 provided on the outer peripheral surface of the cored bar 51. The cored bar 51 includes a central part 51a and outer end parts 51b that are provided on both outer sides of the central part 51a and have a smaller diameter than the central part 51a. The length of the central portion 51 a is shorter than the width of the fixing belt 41. Further, an annular groove 51c is formed in the outer end portions 51b along the outer peripheral surface in the vicinity of the center in the axial direction. The core metal 51 is made of aluminum, iron, or the like.

  The elastic layer 52 is provided around the central portion 51 a of the core bar 51 and has an outer diameter smaller than the inner diameter of the fixing belt 41. Further, on both end faces of the elastic layer 52, stepped portions 52 a that are 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 foamed resin.

  The fixing roller 43 is inserted inside the fixing belt 41, and the end portions of both outer end portions 51 b of the cored bar 51 are respectively supported by bearings 56 via conductive bushes 55. The bearing 56 is supported by a conductive frame (not shown) of the housing 2. Accordingly, the cored bar 51 is grounded to the housing 2 via 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 includes a cylindrical cored bar 44a, an elastic layer 44b provided on the outer peripheral surface of the cored bar 44a, and a release layer (not shown) provided on the outer peripheral surface of the elastic layer 44b. Yes. The pressure roller 44 is supported from below the fixing roller 43 through the fixing belt 41 so as to be in pressure contact with the fixing roller 43 to form a fixing nip 58, and is connected to a driving source (not shown) to rotate. Is done. When the pressure roller 44 is rotated counterclockwise in FIG. 2 by the drive 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. As a result, the sheet that has passed through the fixing nip 58 is conveyed.

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

  The detent member 45 includes a cylindrical main body 71 and a collar portion 72 that projects from one end of the main body 71 in the radial direction. The main body 71 has an inner diameter that is slightly larger than the outer diameter of the outer end 51 b of the core 51 of the fixing roller 41. The collar portion 72 has an outer diameter that is larger than the outer diameter of the fixing belt 41. A slit 73 is formed in the collar portion 72 along the tangential direction of the main body portion 71.

  As shown in FIG. 6, the static elimination member 46 includes a conductive brush 77 and a conductive holder 78 in which the brush 77 is implanted. 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 obtained by bundling a plurality of brush bristles is planted on one side surface in parallel at a predetermined interval. The support portion 78a in which the brush 77 is implanted is bent so as to form 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 a slit 73 formed in the collar portion 72 of the stopper member 45, and the brush 77 is inclined radially outward from the main body 71.

  In this way, the detent member 45 on which the static elimination member 46 is supported is such that the main body portion 71 is rotatably fitted to the outer end portion 51 b of the core metal 51 of the fixing roller 43, and the collar portion 72 is fixed to the fixing belt 41. Are opposed to each other with a predetermined interval. Further, the slip stopper member 45 is restricted from sliding outward in the axial direction by a retaining ring 81 engaged with the annular groove 51c of each outer end portion 51b. Further, by being supported by the cored bar 51 in this way, the stopper member 45 is grounded to the conductive frame of the housing 2 via the cored bar 51.

  The brush 77 protrudes outward from the fixing belt 41 in the free state, but enters the stepped portion 52a of the elastic layer 52 of the fixing roller 43, and the inner surface of the fixing belt 41, that is, the elasticity of the brush hair. In contact with the base material layer.

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

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

  In the fixing device 30 having the above-described configuration, the sheet S on which the toner image is transferred is guided to the sheet entry guide 63 and conveyed to the fixing nip 58. The sheet S is heated by the fixing belt 41 when passing through the fixing nip 58 and is pressed by the pressure roller 44 and the fixing roller 43 to fix the toner image on the sheet S. The sheet S on which the toner is fixed is separated from the fixing belt by the separation 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.

  As shown in FIG. 3, the static elimination member 46 supported by the detent member 45 is in contact with the inner surface (base material layer) of the fixing belt 41. In other words, the fixing belt 41 is grounded to the conductive frame of the housing 2 through the charge removal member 46, the detent member 45, the cored bar 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 are frictionally charged, the charged charges are charged by the charge eliminating member 46, the detent member 45, the core metal 51, the bush 55, and the bearing. The electricity is quickly discharged through 56.

  Further, as shown in FIG. 4, when the fixing belt 41 meanders in one direction (left direction in the figure), the end surface of the fixing belt 41 abuts against the detent member 45 and the meandering of the fixing belt 41 is restricted. Is done. Since the tip of the brush 77 of the static elimination member 46 has a length that can enter the stepped portion 52 a of the elastic layer 52 of the fixing roller 43 and contact the fixing belt 41, the end of the fixing belt 41 in the other direction. The brush 77 also contacts 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 detent member 45 also follows and rotates. Even if the offset member 45 rotates and the static eliminator 46 reaches the fixing nip 58, as shown in FIG. 5, the brush 77 remains on the outer peripheral edge (outside the step 52a) of the elastic layer 52 of the fixing roller 43. Therefore, the fixing nip 58 is not sandwiched between the fixing belt 41 and the pressure roller 44.

  As described above, in the fixing device 30 of the present invention, since the static eliminating member 46 is always in contact with the inner surface of the fixing belt 41, the static eliminating member 46 is used even when the fixing belt 41 is frictionally charged with the paper. Then, the charge is eliminated via the detent member 45, and the fixing belt 41 can be prevented from being charged. Therefore, it is possible to prevent the occurrence of noise due to the discharge of the charged fixing belt 41.

  Further, since the static elimination member 46 is brought into contact with the inner surface of the fixing belt 41, the static elimination of the fixing belt 41 can be reliably performed. As described above, the fixing belt 41 has a three-layer structure including a base material layer, an elastic layer, and a release 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, if it is cut with a cutting blade from the side of the release layer, the release layer wraps around the elastic layer side on the cutting direction side on the cut surface, and the elastic layer further on the cutting direction side. May wrap around the substrate layer on the side. As a result, the conductive base material layer is hardly exposed from the cut surface. That is, the base material layer is hardly exposed on the end face of the fixing belt 41.

  Therefore, for example, when the antistatic stopper member is brought into contact with the end face of the fixing belt 41, the base material layer of the stopper member and the stopper member are not sufficiently in contact with each other, and there is a possibility that the neutralization cannot be performed efficiently. is there.

  Therefore, the neutralization can be efficiently performed by directly bringing the neutralization member 6 into contact with the inside of the fixing belt 41, that is, the base material layer.

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

  Further, since the brush 77 is not sandwiched between the fixing belt 41 and the pressure roller 44 in the fixing nip 58 during the rotation of the detent member 45, the rotation of the detent member 45 is obstructed or the charge eliminating member 46 is 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. However, in other different embodiments, the present invention is applied to an image forming apparatus other than the color printer 1 such as a copying machine, a facsimile machine, and a multifunction machine. You may apply the structure of invention.

  Furthermore, since the above description of the embodiments of the present invention describes preferred embodiments of the fixing device and the image forming apparatus according to the present invention, various technically preferable limitations may be imposed. 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 above-described components in the embodiment of the present invention can be appropriately replaced with existing components and the like, and various variations including combinations with other existing components are possible. The description of the embodiment of the present invention described above does not limit the contents of the invention described in the claims.

1 Color printer (image forming device)
30 fixing device 41 fixing belt 43 fixing roller 44 pressure roller (pressure member)
45 Stoppage member 46 Static elimination member 58 Fixing nip 77 Brush 78 Holder

Claims (5)

An endless fixing belt that is heated by a heat source, a fixing roller that is provided inside the fixing belt so as to be rotatable about a rotation axis, and a pressure that rotates in pressure contact with the fixing roller via the fixing belt A fixing device that forms a fixing nip between the fixing belt and the pressure member,
A conductive detent member disposed opposite to the end surface on the outer side in the rotational axis direction of the end surface of the fixing belt and grounded;
A fixing device, comprising: a neutralizing member provided on the detent member and constantly contacting the fixing belt. The fixing belt has a conductive layer and an elastic layer provided outside the conductive layer,
The fixing device according to claim 1, wherein the static eliminating member is in contact with the conductive layer of the fixing belt.   The fixing device according to claim 1, wherein the neutralizing member is in contact with the fixing belt on the outer side in the rotation axis direction than the fixing nip.   The said static elimination member has an electroconductive brush and the electroconductive holder by which this brush is implanted and supported by the said detent | locking member, The any one of Claims 1-3 characterized by the above-mentioned. The fixing device according to Item 1. An image forming apparatus comprising the fixing device according to claim 1.

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