Fixing device

Abstract

To provide a fixing device that can prevent the flow of an overcurrent in a ground contact due to the breakage of a heater.SOLUTION: A fixing device 5 heats and fixes a toner image formed on a sheet S to the sheet S. The fixing device 5 comprises a heat roller 10 and a ground contact 14. The heat roller 10 heats the toner image formed on the sheet S. The ground contact 14 grounds the heat roller 10. The ground contact 14 has a first conductive member 30, a second conductive member 31, and an insulating member 32. The first conductive member 30 is electrically connected with the heat roller 10. The second conductive member 31 is arranged opposite to the first conductive member 30 and grounds the heat roller 10. The insulating member 32 is arranged sandwiched between the first conductive member 30 and the second conductive member 31 and insulates the first conductive member 30 and the second conductive member 31 from each other.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a fixing device. [Background technology]

[0002] Patent Document 1 discloses a fixing device that prevents damage to the heater. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-103975 Summary of the Invention [Problem to be solved by the invention]

[0004] However, Patent Document 1 does not disclose any measures to be taken when an overcurrent flows through the earth contact due to breakdown of the heater or the like.

[0005] SUMMARY OF THE DISCLOSURE An object of the present invention is to provide a fixing device capable of preventing an overcurrent from flowing to the earth contact due to breakdown of the heater or the like. [Means for solving the problem]

[0006] The fixing device according to the present invention is a fixing device that heats and fixes a toner image formed on a sheet to the sheet. The fixing device includes a heat roller and an earth contact. The heat roller heats the toner image formed on the sheet. The earth contact earths the heat roller. The earth contact has a first conductive member, a second conductive member, and an insulating member. The first conductive member is electrically connected to the heat roller. The second conductive member is disposed opposite the first conductive member and earths the heat roller. The insulating member is disposed between the first conductive member and the second conductive member and insulates the first conductive member from the second conductive member. Effect of the Invention

[0007] According to the fixing device of the present invention, it is possible to prevent an overcurrent from flowing to the earth contact due to breakdown of the heater or the like. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing an image forming apparatus including a fixing device according to an embodiment of the present invention; [Diagram 2] 2 is a diagram illustrating a structure of a fixing device according to the embodiment; [Diagram 3] FIG. 4 is a diagram illustrating a comparative example of the fixing device according to the embodiment. [Figure 4] FIG. 2 is a diagram illustrating a detailed structure of a fixing device according to the embodiment. [Diagram 5] FIG. 2 is a diagram illustrating a detailed structure of a fixing device according to the embodiment. [Figure 6] FIG. 2 is a diagram illustrating a detailed structure of a fixing device according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference symbols and the description will not be repeated. In this embodiment, the drawings show an X-axis, a Y-axis, and a Z-axis that are perpendicular to each other. The Z-axis is parallel to the vertical plane, and the X-axis and the Y-axis are parallel to the horizontal plane.

[0010] In this embodiment, the conveying direction of the sheet S in the image forming unit 4 may be referred to as a sub-scanning direction, and the X-axis direction perpendicular to the sub-scanning direction may be referred to as a main scanning direction.

[0011] An image forming apparatus 1 having a fixing device 5 according to an embodiment of the present invention will be described with reference to Figs. 1 to 6. Fig. 1 is a diagram showing an image forming apparatus 1 including a fixing device 5 according to an embodiment of the present invention. Fig. 2 is a diagram showing a structure of the fixing device 5 according to the present embodiment. Fig. 3 is a diagram showing a comparative example of the fixing device 5 according to the present embodiment. Figs. 4 to 6 are diagrams showing a detailed structure of the fixing device 5 according to the present embodiment.

[0012] The image forming apparatus 1 according to this embodiment is of an electrophotographic type and includes a sheet feeding device 2, a sheet conveying device 3, an image forming section 4, a fixing device 5, a sheet discharge section 6, a power supply section, a drive section, and a control section.

[0013] The sheet feeding device 2 includes, for example, a sheet tray and a pickup roller.

[0014] The sheet transport device 3 includes, for example, a transport path, a transport roller, and a transport motor.

[0015] The sheet S is conveyed along the conveying path.

[0016] The transport rollers are disposed in the transport path and transport the sheet S.

[0017] The transport motor rotates the transport roller.

[0018] Next, as shown in FIG. 1, the image forming unit 4 forms a toner image (not shown) on the sheet S based on the document image data.

[0019] The image forming unit 4 includes, for example, an image data acquiring unit, a photosensitive drum, a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit.

[0020] The image data acquisition unit acquires image data from, for example, a scanner, a personal computer, a server, a cloud, etc. The image data acquisition unit may be realized, for example, by an ASIC.

[0021] The photoconductor drum has a drum shape and a rotation axis. The photoconductor drum rotates around the rotation axis. The photoconductor drum has a photosensitive layer on the outer circumferential surface side.

[0022] The charging section charges the photosensitive layer of the photosensitive drum to a predetermined potential.

[0023] The exposure unit irradiates the photosensitive layer of the photoconductor drum with laser light to expose it. The exposure unit exposes the photoconductor drum based on image data. As a result, an electrostatic latent image is formed on the photoconductor drum. An example of the exposure unit is an LED (Light Emitting Diode).

[0024] The developing unit contains, for example, a two-component developer containing a carrier made of a magnetic material and a toner, and develops the electrostatic latent image formed on the photoconductor drum with the toner to form a toner image on the photoconductor drum.

[0025] The transfer section transfers the toner image on the photosensitive drum onto the sheet S.

[0026] The cleaning unit removes residual toner remaining on the photosensitive drum after transfer. The sheet S on which the toner image has been formed by the image forming unit 4 is conveyed to a fixing device 5.

[0027] Next, the fixing device 5 will be described with reference to Fig. 2. The fixing device 5 heats and fixes the toner image formed on the sheet S to the sheet S.

[0028] The fixing device 5 further includes a heat roller 10 and a conductive bearing 13. The heat roller 10 heats the toner image formed on the sheet S. The conductive bearing 13 supports the heat roller 10 rotatably.

[0029] 2, the fixing device 5 has a heat roller 10, a press roller 11, a heater 12, a conductive bearing 13, a ground contact 14, and a blocking member 15. The ground contact 14 and the blocking member 15 will be described in detail with reference to FIGS. 4 to 6.

[0030] The heat roller 10 heats the toner image formed on the sheet S. The heat roller 10 is a hollow cylindrical roller. The heat roller 10 is an example, and may be a belt.

[0031] The press roller 11 is pressed against the heat roller 10 to form a nip portion with the heat roller 10. The press roller 11 is rotationally driven by a drive unit, and forms a nip portion with the heat roller 10, thereby rotating the heat roller 10.

[0032] The sheet S passes through the nip formed between the heat roller 10 and the press roller 11. The toner image formed on the sheet S passing through the nip is heated by the heat roller 10. The heated and melted toner is pressed onto the sheet S by the press roller 11, and a toner image is formed on the sheet S.

[0033] The fixing device 5 further includes a heater 12. The heater 12 generates heat when power is supplied from a power supply unit, and heats the heat roller 10.

[0034] The heater 12 is supplied with power from a power supply unit and heats the heat roller 10. The heater 12 is disposed close to the inner circumferential surface of the heat roller 10. The sheet S conveyed to the sheet conveying device 3 passes through the nip portion and is heated by the heater 12, and the toner image is fixed.

[0035] The heater 12 may have a halogen lamp 20 and a filament 21. The filament 21 generates heat when power is supplied from a power supply unit. The filament 21 is disposed inside the halogen lamp 20. That is, the halogen lamp 20 has the filament 21 disposed in the longitudinal direction inside a glass tube formed into a substantially rod-like (substantially cylindrical) shape in which halogen gas is sealed. The filament 21 is wound in a coil shape.

[0036] The halogen lamp 20 further has a pair of electrodes at both axial ends of the glass tube. The filament 21 is connected to the pair of electrodes. The filament 21 generates heat when power is supplied from a power source via the pair of electrodes.

[0037] The filament 21 is made of tungsten, for example. When a current flows through the filament 21, the filament 21 is heated to 2,300° C. due to the electrical resistance of the filament 21 itself, and becomes incandescent.

[0038] The halogen lamp 20 heats the heat roller 10 from the inside by utilizing infrared light emitted from a filament 21. Instead of the halogen lamp 20, a carbon heater or the like may be used.

[0039] A control unit (not shown) controls the power supply from the power supply unit to the heater 12. The control unit turns ON / OFF the power supply from the power supply unit to the heater 12. The control unit controls the amount of current flowing through the filament 21 so that the surface temperature of the heat roller 10 is, for example, 160°C to 180°C.

[0040] As shown in FIG. 2, the conductive bearing 13 supports the heat roller 10 so that the heat roller 10 can rotate.

[0041] Next, the ground contact 14 and the interrupter member 15 will be described in detail with reference to FIGS.

[0042] First, the ground contact 14 grounds the heat roller 10. As shown in Figures 4 and 5, the ground contact 14 has a first conductive member 30, a second conductive member 31, and an insulating member 32.

[0043] 4, the first conductive member 30 may have a first slit 40. The second conductive member 31 may have a second slit 41.

[0044] The first conductive member 30 (first leaf spring 30) is electrically connected to the heat roller 10. The second conductive member 31 (second leaf spring 31) is disposed opposite the first conductive member 30 and grounds the heat roller 10.

[0045] The first conductive member 30 may be described as a first leaf spring 30. That is, the first conductive member 30 may be a leaf spring having electrical conductivity. The first conductive member 30 is made of stainless steel, nickel, molybdenum, copper, or the like.

[0046] The first conductive member 30 is electrically connected to the heat roller 10.

[0047] Insulating member 32 (insulating sheet 32) is disposed between first conductive member 30 and second conductive member 31, and insulates first conductive member 30 and second conductive member 31 from each other.

[0048] The insulating member 32 may be referred to as an insulating sheet 32. That is, the insulating member 32 may be a sheet-like member. An example of the insulating member 32 is a polyimide epoxy resin.

[0049] The insulating member 32 is a sheet-like member having a predetermined thickness, and is interposed between a first surface facing the first conductive member 30 and a second surface facing the second conductive member 31. The distance between the first surface of the insulating member 32 facing the first conductive member 30 and the second surface facing the second conductive member 31 may be 0.5 mm.

[0050] The earth contact 14, by means of the insulating member 32, suppresses an overcurrent in the conductive bearing 13 that occurs when the heater 12 comes into contact with the conductive bearing 13. The earth contact 14, by means of the insulating member 32, suppresses an overcurrent in the conductive bearing 13 that occurs due to the power supplied to the heater 12.

[0051] The earth contact 14 suppresses an overcurrent in the conductive bearing 13 that occurs when the filament 21 comes into contact with the heat roller 10. The earth contact 14 suppresses an overcurrent in the conductive bearing 13 that occurs when the filament 21 comes into contact with the conductive bearing 13.

[0052] The blocking member 15 is disposed between the first conductive member 30 and the second conductive member 31, and blocks an overcurrent flowing through the fixing device 5.

[0053] The first slit 40 of the first conductive member 30 supports one end of the blocking member 15 .

[0054] The first conductive member 30 is electrically connected to the conductive bearing 13 .

[0055] The second conductive member 31 may be described as a second leaf spring 31. That is, the second conductive member 31 may be a leaf spring having electrical conductivity. The second conductive member 31 is made of stainless steel, nickel, molybdenum, copper, or the like.

[0056] The second slit 41 of the second conductive member 31 supports the other end of the blocking member 15 .

[0057] The blocking member 15 is attached at the attachment position shown by the dotted line in FIG. 4 by attaching one end to the first slit 40 of the first conductive member 30 and the other end to the second slit 41 of the second conductive member 31.

[0058] Next, the function of the ground contact 14 of the fixing device 5 according to this embodiment will be described.

[0059] As described above with reference to FIG. 2, the heater 12 is disposed inside the heat roller 10, and the heater 12 includes a halogen lamp 20 having a filament 21 disposed therein.

[0060] The halogen lamp 20 is often made of a glass tube, and therefore may be damaged if the fixing device 5 is dropped, for example.

[0061] If the halogen lamp 20 is damaged by dropping the fixing device 5, for example, the filament 21 arranged inside the halogen lamp 20 may become exposed and come into contact with the inner surface of the heat roller 10, which is made of a metal member.

[0062] Here, as a comparative example, Fig. 3 will be referred to. As shown in Fig. 3, when the fixing device 5 is grounded by a single leaf spring, if the filament 21 comes into contact with the inner peripheral surface of the heat roller 10, a current flows from the filament 21 through the conductive bearing 13, which is grounded by a ground member, and the conductive bearing 13 may ignite due to an overcurrent.

[0063] As a measure to prevent the conductive bearing 13 from catching fire, it is possible to provide a cutoff member 15 such as a fuse on the ground member as shown in Fig. 4. However, the cutoff member 15 such as a fuse may fall off from the ground member due to vibration or dropping of the image forming apparatus 1.

[0064] If the interrupter 15 such as a fuse falls off from the earth member, the conductive bearing 13 cannot be grounded.

[0065] Therefore, in this embodiment, as shown in Figure 5, two leaf springs, a first conductive member 30 and a second conductive member 31, are provided as a configuration that performs the earthing function, and an insulating member 32 is arranged between the first conductive member 30 and the second conductive member 31 together with a blocking member 15.

[0066] By disposing the insulating member 32 as a thin sheet member between the first conductive member 30 and the second conductive member 31, even if the cutoff member 15 such as a fuse falls off the fixing device 5, when the first conductive member 30 side becomes at a high potential, a discharge occurs in the gap formed by the insulating member 32 and the second conductive member 31. Therefore, it is possible to prevent the heat roller 10 from being charged and becoming at a high potential.

[0067] Here, if the insulating member 32 is configured to be thick, the insulation between the first conductive member 30 and the second conductive member 31 is improved, but the surface potential of the heat roller 10 increases to 4 to 5 kV due to charging, making it more likely that image defects will occur in the toner image on the sheet S.

[0068] In contrast, as shown in FIG. 4, when a cut-off member 15 such as a fuse is attached to the first conductive member 30 and the second conductive member 31, the cut-off member 15 establishes electrical conductivity between the first conductive member 30 and the second conductive member 31, and the electrostatic charge of the heat roller 10 is earthed via the conductive bearing 13, so that the surface potential of the heat roller 10 is suppressed to, for example, 100V to 500V.

[0069] In this embodiment, when a thin sheet-like insulating member 32 is placed between the first conductive member 30 and the second conductive member 31 to provide insulation, even if a cut-off member 15 such as a fuse falls off from the fixing device 5, if the charged charge on the heat roller 10 becomes excessive, some of the charge is grounded by discharge between the first conductive member 30 and the second conductive member 31, and the surface potential of the heat roller 10 during image formation operation is suppressed to, for example, approximately 1.5 kV or less.

[0070] Therefore, it is possible to prevent the conductive bearing 13 from catching fire with a normal AC voltage of 240 V. Although the surface potential due to charging during image formation of the heat roller 10 rises from 100 to 500 V to a maximum of 1.5 kV, this is a lower voltage than when completely insulated and not grounded, so image defects are minor.

[0071] 5, the fixing device 5 includes a housing. The housing has a ground contact 14. The housing of the fixing device 5 has a protrusion for mounting the ground contact 14. The first conductive member 30, the second conductive member 31, and the insulating member 32 have holes that fit into the protrusions.

[0072] The ground contact 14 is formed by stacking a first conductive member 30, an insulating member 32, and a second conductive member 31 in this order from the side closest to the housing of the fixing device 5, and fastening them with fasteners as shown in FIG.

[0073] The outer shape of the insulating member 32 is formed slightly larger than the outer shape of the mutually facing surfaces of the first conductive member 30 and the second conductive member 31. The diameters of the holes of the first conductive member 30, the second conductive member 31, and the insulating member 32 that fit into the convex portions are formed to be larger than the diameter of the convex portions by approximately the fitting tolerance. At the outer edge portions of the facing surfaces of the first conductive member 30 and the second conductive member 31, there is a possibility that they may separate in the overlapping direction due to deformation caused by an external force, but at the holes that fit into the convex portions, the separation in the overlapping direction is restricted by the fasteners. Therefore, the insulation distance between the edges of the holes of the first conductive member 30 and the second conductive member 31 is kept constant by the thickness of the insulating member 32.

[0074] Furthermore, a breaking member 15 such as a fuse is attached to the first slit 40 of the first conductive member 30 and to the second slit 41 of the second conductive member 31 .

[0075] According to this embodiment, it is possible to prevent an overcurrent from flowing through the conductive bearing 13 via the ground contact 14, and to prevent the fixing device 5 from catching fire. Furthermore, even if the blocking member 15 becomes detached from the first conductive member 30 or the second conductive member 31, the insulating member 32 can prevent the fixing device 5 from catching fire, and it is also possible to prevent the heat roller 10 from being charged to a high potential during an image forming operation.

[0076] Furthermore, by configuring the earth contact 14 with the first conductive member 30 and the second conductive member 31 and disposing the insulating member 32 between the first conductive member 30 and the second conductive member 31, it is possible to provide an appropriate insulation resistance between the conductive bearing 13 of the heat roller 10 and the earth. In other words, when a high voltage potential is applied between the first conductive member 30 and the second conductive member 31, a discharge occurs between the edges of the hole, and the potential difference is alleviated.

[0077] Furthermore, by setting the distance between the first surface facing the first conductive member 30 and the second surface facing the second conductive member 31 to 0.5 mm depending on the thickness of the insulating member 32, even if an AC of 240 V is applied to the fixing device 5 from the power supply unit, the fixing device 5 can be suitably insulated and static electricity of the heat roller 10 can be suitably discharged. The insulating member 32 may be formed of a sheet member having a thickness of 0.5 mm, or may be formed of a sheet member having a thickness of 0.25 mm and used in a two-ply configuration.

[0078] The sheet discharge section 6 discharges the sheet S to the outside of the housing of the image forming apparatus 1. The sheet discharge section 6 may have a discharge roller and a discharge tray. The discharge roller discharges the sheet S, which has been transported from the fixing device 5 by the transport roller, to the discharge tray. The discharge tray stacks the discharged sheet S.

[0079] The power supply unit also supplies power to each component of the image forming apparatus 1. In particular, the power supply unit supplies power to the filament 21 of the fixing device 5.

[0080] The drive unit drives each part of the image forming apparatus 1. In particular, the drive unit drives the press roller 11 of the fixing device 5. An example of the drive unit is a motor.

[0081] The control device controls each part of the image forming apparatus 1. In particular, the control device controls the power and temperature supplied to the heater 12 of the fixing device 5. An example of the control device is a CPU (Central Processing Unit).

[0082] The embodiments of the present invention have been described above with reference to the drawings. However, the present invention is not limited to the above embodiments, and can be implemented in various forms without departing from the scope of the present invention. The drawings are mainly schematic illustrations of the respective components for ease of understanding, and the number of each component shown in the drawings may differ from the actual number due to the convenience of drawing. Furthermore, the components shown in the above embodiments are merely examples, and are not particularly limited, and various modifications are possible without substantially departing from the effects of the present invention. [Industrial Applicability]

[0083] The present invention can be used in the field of fixing devices. [Explanation of symbols]

[0084] 1. Image forming device 5 Fixing device 10 Heat Roller 11 Press roller 12 Heater 13 Conductive bearings 14 Earth Contact 15 Blocking member 20 Halogen lamp 21 Filament 30 First conductive member 31 Second conductive member 32 Insulating materials 40 First Slit 41 Second Slit

Claims

1. A fixing device that heats and fixes a toner image formed on a sheet to the sheet, The fixing device is a heat roller for heating the toner image formed on the sheet; an earth contact for earthing the heat roller; A conductive bearing that rotatably supports the heat roller; a heater that receives power from a power supply unit to generate heat and heat the heat roller; Equipped with The earth contact is A first conductive member electrically connected to the heat roller; A second conductive member that is disposed opposite the first conductive member and grounds the heat roller; an insulating member disposed between the first conductive member and the second conductive member and insulating the first conductive member from the second conductive member; having The earth contact, by means of the insulating member, suppresses an overcurrent in the conductive bearing caused by power supplied to the heater.

2. 2 . The fixing device according to claim 1 , wherein the insulating member is a sheet-like member having a predetermined thickness and interposed between a first surface facing the first conductive member and a second surface facing the second conductive member.

3. a housing in which the ground contact is disposed, The housing has a protrusion for mounting the ground contact, 3. The fixing device according to claim 1, wherein the first conductive member, the second conductive member and the insulating member each have a hole into which the protrusion fits.

4. the heater has a filament that generates heat when power is supplied from the power supply unit, The fixing device according to claim 1 , wherein the ground contact suppresses an overcurrent in the conductive bearing caused by the filament coming into contact with the heat roller.

5. a cut-off member disposed between the first conductive member and the second conductive member and configured to cut off an overcurrent flowing through the fixing device; the first conductive member has a first slit that supports one end of the blocking member, The fixing device according to claim 1 , wherein the second conductive member has a second slit that supports the other end of the blocking member.

6. An image forming apparatus comprising the fixing device according to claim 1 .

Images