Heating device, fixing device, and image forming device

Abstract

The heating device includes a planar heater, a heating rotating body, a pressurizing rotating body, and one or more anti-static components. The planar heater includes a substrate and a resistance heating element. The heating rotating body is in contact with the heater and includes a conductive layer. The pressurizing rotating body pressurizes the heating rotating body and has an outer surface comprising a conductive material. One or more anti-static components contact the conductive layer and the outer surface of the pressurizing rotating body.

Description

Technical Field

[0001] Embodiments of this disclosure relate to a heating apparatus, a fixing apparatus, and an image forming apparatus. Background Technology

[0002] The heating device in the fixing unit includes a fixing belt as a heating rotating component and a pressure roller as a pressure rotating component. When the sheet passes through the fixing clamp between the fixing belt and the pressure roller, the toner on the sheet is heated and pressurized.

[0003] A flat heater, serving as the heating element for the fixing belt, is disposed inside the ring of the fixing belt. Heat is generated when an alternating current (AC) voltage is applied to a resistive heating element on the substrate of the heater. The heater heats the fixing belt by contacting its inner surface, for example, via an insulating layer disposed within the heater.

[0004] Image forming apparatuses, including such fixing devices, may have several electrical problems.

[0005] For example, the surface layers of the fixing belt and pressure roller become charged due to friction caused by the rotation of the fixing belt and pressure roller through the fixing clamp. If this charging is not reduced, the toner image on the sheet will electrostatically shift during the fixing process, resulting in abnormal images. This problem is particularly prone to occur in low-humidity environments or when images are formed on sheets with high surface resistance due to the coating agent.

[0006] Furthermore, in the configuration where AC voltage is applied to the heater, the insulating layer in the heater and the rubber layer of the fixing belt are equivalent to capacitors, and the AC voltage is applied to the fixing clamp via the fixing belt. When the sheet comes into contact with both the transfer clamp and the fixing clamp, the AC voltage is transmitted to the transfer clamp via the sheet. As a result, the AC voltage affects the transfer electric field and causes periodic density non-uniformity in the transferred image, i.e., so-called striped images. For example, this problem becomes particularly significant in high humidity environments or when using thin paper sheets as sheets with low resistance.

[0007] For example, in Patent Document (PTL) 1, the fixing inlet guide is positioned upstream of the fixing clamp in the sheet transport direction. A resistor and a capacitor are connected in parallel to the fixing inlet guide, and the fixing inlet guide is grounded via the resistor and capacitor. This allows the AC voltage flowing from the fixing belt to the transfer clamp through the paper to flow to the fixing inlet guide, and prevents the occurrence of striped images caused by the AC voltage propagating to the transfer side.

[0008] However, the configuration of PTL 1 did not completely solve the aforementioned electrical problems.

[0009] Citation List

[0010] Patent documents

[0011] Patent Document 1: Japanese Unexamined Patent Application No. 2015-084084 Summary of the Invention

[0012] Technical issues

[0013] The purpose of this disclosure is to solve electrical problems occurring in and around heating devices.

[0014] Solution to the problem

[0015] The heating device according to embodiments of this disclosure includes a planar heater, a heating rotating body, a pressurizing rotating body, and one or more anti-static components. The planar heater includes a substrate and a resistance heating element. The heating rotating body contacts the heater and includes a conductive layer. The pressurizing rotating body pressurizes the heating rotating body and has an outer surface comprising a conductive material. One or more anti-static components contact the conductive layer and the outer surface of the pressurizing rotating body.

[0016] Effects of the present invention

[0017] According to embodiments of this disclosure, electrical problems occurring in or around the heating device can be prevented. Attached Figure Description

[0018] The accompanying drawings are intended to illustrate exemplary embodiments of the invention and should not be construed as limiting its scope. Unless explicitly stated otherwise, the drawings should not be considered to be drawn to scale. Furthermore, in all the drawings, the same or similar reference numerals denote the same or similar parts.

[0019] Figure 1 The diagram shown is a schematic representation of the configuration of an image forming apparatus according to an embodiment of the present disclosure.

[0020] Figure 2 The diagram shown is a schematic representation of the fixing apparatus according to an embodiment of the present disclosure.

[0021] Figure 3A The image shown is a top view of the heater according to an embodiment of this disclosure. Figure 3B The image shown is along Figure 3A The sectional view of the heater is taken by line AA.

[0022] Figure 4 The image shows the installation. Figure 3A A perspective view of the heater and the connector on the heater retaining component.

[0023] Figure 5 The diagram shows a circuit that supplies power to the heater.

[0024] Figure 6The image shown is in relation to Figure 2 A diagram illustrating the propagation of AC voltage from the fixing clamp to the transfer clamp in different fixing devices.

[0025] Figure 7 The image shown is a perspective view of the static elimination components in contact with the fixing belt and the pressure roller.

[0026] Figure 8 The diagram shows a static removal component in contact with the fixing belt and the pressure roller.

[0027] Figure 9 The figure shown is a perspective view of the current-eliminating component according to an embodiment of the present disclosure.

[0028] Figure 10 The image shown is a perspective view of a fixing device including a holding member for holding the electric discharge component, according to an embodiment of the present disclosure.

[0029] Figure 11 The image shown is a side cross-sectional view of a fixing apparatus including a heat spreader according to an embodiment of the present disclosure.

[0030] Figure 12 The diagram shown is a schematic representation of the configuration of a monochrome image forming apparatus according to an embodiment of the present disclosure. Detailed Implementation

[0031] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0032] In describing the embodiments shown in the accompanying drawings, specific terms have been used for clarity. However, the disclosure of this specification is not intended to be limited to the selected specific terms, and it should be understood that each specific element includes all technical equivalents that have similar functions, operate in a similar manner, and achieve similar results.

[0033] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. The same reference numerals will be used for the same parts or equivalents, and the description of these components may be simplified or omitted. As an example of a heating device, a fixing apparatus for fixing a toner image onto a sheet will be described below.

[0034] Figure 1The image forming apparatus 100 shown includes four imaging units 1Y, 1M, 1C, and 1Bk detachably mounted to its main body. Except for containing different color developers, namely yellow (Y), magenta (M), cyan (C), and black (Bk) toners, the imaging units 1Y, 1M, 1C, and 1Bk have substantially the same configuration. The color of the developer corresponds to the color decomposition components of a panchromatic image. Each imaging unit 1Y, 1M, 1C, and 1Bk includes a drum-shaped photoreceptor 2 as an image carrier, a charging device 3, a developing device 4, and a cleaning device 5. The charging device 3 charges the surface of the photoreceptor 2. The developing device 4 supplies the toner, as a developer, to the surface of the photoreceptor 2 to form a toner image. The cleaning device 5 cleans the surface of the photoreceptor 2.

[0035] The image forming apparatus 100 includes an exposure unit 6, a sheet supply unit 7, a transfer unit 8, a fixing unit 9 (which serves as a heating unit), and a sheet ejection unit 10. The exposure unit 6 exposes the surface of the photoreceptor 2, forming an electrostatic latent image on the surface of the photoreceptor 2. The sheet supply unit 7 supplies a sheet P, which serves as a recording medium, to the sheet transport path B. The transfer unit 8 transfers the toner image formed on the photoreceptor 2 onto the sheet P. The fixing unit 9 fixes the toner image transferred onto the sheet P onto the surface of the sheet P. The sheet ejection unit 10 ejects the sheet P to the outside of the image forming apparatus 100. Imaging units 1Y, 1M, 1C, and 1Bk, including the photoreceptor 2, charging unit 3, exposure unit 6, and transfer unit 8, constitute an imaging device that forms an image on the sheet P.

[0036] The transfer apparatus 8 includes an intermediate transfer belt 11 in an annular shape serving as an intermediate transfer component, four primary transfer rollers 12 serving as primary transfer components, a secondary transfer roller 13 serving as a secondary transfer component, and a counter roller 14. The intermediate transfer belt 11 is tensioned and mounted by the multiple rollers. Each of the four primary transfer rollers 12 transfers the toner image on each photoreceptor 2 onto the intermediate transfer belt 11. The secondary transfer roller 13 transfers the toner image transferred onto the intermediate transfer belt 11 onto the sheet P. The four primary transfer rollers 12 contact each photoreceptor 2 via the intermediate transfer belt 11. Thus, the intermediate transfer belt 11 contacts each photoreceptor 2, forming a primary transfer clamping portion between them. The secondary transfer roller 13 contacts the counter roller 14 via the intermediate transfer belt 11. Thus, a secondary transfer clamping portion N1, serving as a clamping or transfer portion, is formed between the secondary transfer roller 13 and the intermediate transfer belt 11. The opposing roller 14 is the roller that tensions and supports the intermediate transfer belt 11.

[0037] The timing roller pair 15 is set along the sheet conveying path B from the sheet supply device 7 to the secondary transfer clamping part N1.

[0038] Reference Figure 1This will be used to explain the printing process performed by the image forming apparatus 100 described above.

[0039] When the image forming apparatus 100 receives a command to start printing, the driver activates each of the imaging units 1Y, 1M, 1C, and 1Bk. Figure 1 The photoreceptor 2 is driven and rotated clockwise. The charging device 3 charges the surface of the photoreceptor 2 to a uniform high potential. Then, the exposure device 6 exposes the surface of each photoreceptor 2 based on the image data of the original document read by the document reading device or the print data to be printed indicated by the terminal. As a result, the potential of the exposed portion on the surface of each photoreceptor 2 decreases, and an electrostatic latent image is formed on the surface of each photoreceptor 2. The developing device 4 supplies toner to the electrostatic latent image formed on the photoreceptor 2, and forms a toner image thereon.

[0040] The toner images formed on each photoreceptor 2 are transferred to the primary transfer clamping section at each primary transfer roller 12 according to the rotation of each photoreceptor 2. The toner images are sequentially transferred and superimposed onto the rollers. Figure 1 A full-tone toner image is formed on an intermediate transfer belt 11 that is driven to rotate counterclockwise. Then, according to the rotation of the intermediate transfer belt 11, the full-tone toner image formed on the intermediate transfer belt 11 is conveyed to a secondary transfer clamping section defined by a secondary transfer roller 13. The full-tone toner image is transferred onto a sheet P conveyed to the secondary transfer clamping section. The sheet P is supplied by a sheet supply device 7. A timing roller pair 15 temporarily stops the sheet P supplied from the sheet supply device 7. Thereafter, when the full-tone toner image formed on the intermediate transfer belt 11 reaches the secondary transfer clamping section, the timing roller pair 15 conveys the sheet P to the secondary transfer clamping section. Thus, the full-tone toner image is transferred and carried onto the sheet P. After the toner image is transferred onto the intermediate transfer belt 11, a cleaning device 5 removes any remaining toner on the photoreceptor 2.

[0041] The sheet P, on which a full-tone toner image has been transferred, is conveyed to the fixing device 9, which fixes the full-tone toner image onto the sheet P. Then, the sheet ejection device 10 ejects the sheet P outside the image forming apparatus 100, thus completing a series of printing processes.

[0042] Next, the composition of the fixing device will be explained in more detail.

[0043] like Figure 2As shown, the fixing apparatus 9 according to this embodiment includes an annular fixing belt 20 as a fixing rotation member or fixing component, a pressure roller 21 as a pressure rotation member or pressure member, a heater 22 as a heating element, a heater holder 23 as a holding member, a support member 24 as a support member, and a thermistor 25 as a temperature detection mechanism. The pressure roller 21 contacts the outer peripheral surface of the fixing belt 20 to form a fixing clamping portion N2 as a clamping portion. The heater 22 heats the fixing belt 20. The heater holder 23 holds the heater 22. The support member 24 supports the rear side of the heater holder 23. The fixing belt 20, pressure roller 21, heater 22, heater holder 23, and support member 24 are arranged perpendicular to the... Figure 2 It extends in the direction of the paper surface. Hereinafter, this direction will be referred to as the long side direction of each component or simply the long side direction. The long side direction is also the axial direction of the pressure roller 21 and the width direction of the sheet P passing through the fixing device 9.

[0044] The fixing belt 20 includes a tubular substrate made of polyimide (PI) and has an outer diameter of, for example, 25 mm and a wall thickness in the range of 50 micrometers (μm) to 70 μm. A release layer with a thickness of 7 μm to 20 μm is formed on the outermost layer of the fixing belt 20. An elastic layer made of rubber with a thickness of 100 μm to 300 μm is provided between the substrate and the release layer. The substrate of the fixing belt 20 can be made of a heat-resistant resin such as polyetheretherketone (PEEK) or stainless steel such as nickel (Ni) or stainless steel (SUS) instead of polyimide. The inner surface of the fixing belt 20 can be coated with, for example, polyimide or polytetrafluoroethylene (PTFE). The fixing belt 20 is a heated component heated by the heater 22 and is also a heating component for heating the sheet (with toner) in the fixing clamping part N2.

[0045] The outer diameter of the pressure roller 21 is, for example, 25 mm. The pressure roller 21 includes a core rod 21a, an elastic layer 21b, and a release layer 21c. The core 21a is a solid core rod made of iron. The elastic layer 21b covers the circumferential surface of the core rod 21a. The elastic layer 21b is made of silicone rubber and has a thickness of, for example, from 3.5 mm to 4.0 mm. The release layer 21c covers the outer circumferential surface of the elastic layer 21b. To improve the release properties of the pressure roller 21, the release layer 21c is preferably a fluoropolymer resin layer, for example, from approximately 30 μm to approximately 50 μm.

[0046] The pressure roller 21 is forced towards the fixing belt 20 by the force-applying member and pressed against the heater 22 via the fixing belt 20. Thus, a fixing clamping portion N2 is formed between the fixing belt 20 and the pressure roller 21. Furthermore, the driver drives and rotates the pressure roller 21. When the pressure roller 21 moves along... Figure 2 When rotating in the direction indicated by the middle arrow, the rotation of the pressure roller 21 drives the fixing belt 20 along the direction of the friction between them. Figure 2Rotate in the direction indicated by the middle arrow.

[0047] Heater 22 is a planar heating element extending along its long side. Heater 22 heats the inner surface of the fixing tape 20 by the heating of the resistance heating element 40 on the substrate 30. The detailed structure of heater 22 will be described later.

[0048] The heater holder 23 and the support 24 are disposed inside the loop of the fixing belt 20. The support 24 is made of a metal tubing component, and the two side plates of the fixing unit 9 support both ends of the support 24. The support 24 supports the heater holder 23 and the heater 22 held by the heater holder 23. Therefore, the heater 22 is reliably subjected to the pressure applied by the pressure roller 21 pressing against the fixing belt 20, and a fixing clamping part N2 is stably formed between the fixing belt 20 and the pressure roller 21.

[0049] Since the heater holder 23 is heated to a high temperature by heat from the heater 22, the heater holder 23 is preferably made of a heat-resistant material. The heater holder 23, made of a heat-resistant resin with low thermal conductivity, such as liquid crystal polymer (LCP), reduces heat transfer from the heater 22 to the heater holder 23, thus allowing the heater 22 to effectively heat the fixing belt 20.

[0050] The heater holder 23 has a protrusion 23a partially disposed along its short side and protruding toward the heater 22. The heater holder 23 contacts the heater 22 at the protrusion 23a. The protrusion 23a reduces the contact area between the heater holder 23 and the heater 22, thereby reducing the heat transferred from the heater 22 to the heater holder 23. However, in some embodiments, the entire surface of the heater holder 23 in the lateral direction can contact the heater 22 without the protrusion 23a. This configuration can increase the heat transferred from the heater 22 to the heater holder 23 and reduce the temperature rise of the heater 22 and the fixing belt 20.

[0051] Thermistor 25 is in contact with the back of substrate 30 to detect the temperature of substrate 30.

[0052] When the fixing device 9 according to this embodiment starts printing, the pressure roller 21 is driven to rotate, and as... Figure 2 The rotation of the pressure roller 21, as shown, causes the fixing belt 20 to rotate. When power is supplied to the resistive heating element 40 of the heater 22, the heater 22 heats the fixing belt 20. After the temperature of the fixing belt 20 reaches a predetermined target temperature (i.e., the fixing temperature), the sheet P carrying the unfixed toner image is conveyed to the fixing clamping section N2 between the fixing belt 20 and the pressure roller 21. As a result, the unfixed toner image is heated and pressurized and then fixed onto the sheet P.

[0053] Next, the configuration of heater 22 will be described in more detail with reference to FIG3. Figure 3A The image shown is a top view of heater 22. Figure 3B The image shown is along Figure 3A The sectional view of heater 22 taken by line AA.

[0054] Heater 22 from heater holder 23 side ( Figure 2 The left side of the structure includes, in sequence, a first insulating protective layer 31, a first insulating glass layer 32, a substrate 30, a second insulating protective layer 33, a conductor layer 34, and a second insulating glass layer 35.

[0055] The substrate 30 is a plate-shaped component extending along its long side. In this embodiment, the length of the substrate 30 is set to 270 mm, the length along its short side is set to 8 mm, and the height is set to 0.3 mm. The heater 22 has its long side extending along its short side. Figure 3A The direction indicated by the double-headed arrow X in the diagram is the direction of the shorter side of heater 22. Figure 3A The direction indicated by the double-headed arrow Y. The short side direction of heater 22 is along the surface of the substrate 30 on which the resistive heating element 40 is disposed, and is a direction that intersects with the long side direction of heater 22 (orthogonal in this embodiment).

[0056] In this embodiment, the substrate 30 is made of stainless steel. In some embodiments, the substrate 30 may be made of an iron-based alloy, an aluminum alloy, or a copper alloy. Alternatively, the substrate 30 may also be made of ceramics such as alumina or aluminum nitride.

[0057] The conductor layer 34 is formed on the substrate 30 via a second insulating protective layer 33. This configuration ensures insulation between the conductor layer 34 and the substrate 30. The conductor layer 34 is provided with a resistive heating element 40, electrodes 41a and 41b (collectively referred to as electrodes 41 when no distinction is needed), and a power supply line 42.

[0058] The resistive heating element 40 is manufactured, for example, by mixing silver-palladium (AgPd), glass powder, etc., into a paste. This paste is applied to a substrate 30 by screen printing or the like. The substrate 30 is then fired to form the resistive heating element 40. In this embodiment, each resistive heating element 40 has a resistance value of 10 Ω at room temperature. In addition to the materials described above, the material of the resistive heating element 40 may include resistive materials such as silver alloy (AgPt) or ruthenium oxide (RuO2). Silver (Ag), silver-palladium (AgPd), etc., can be used as the materials for the power supply lines 42 and the electrodes 41. The power supply lines 42 and the electrodes 41 are formed by screen printing. The power supply lines 42 are composed of conductors having a resistance value smaller than that of the resistive heating element 40.

[0059] The first insulating protective layer 31, the first insulating glass layer 32, the second insulating protective layer 33, the conductive layer 34, and the second insulating glass layer 35 are, for example, made of heat-resistant glass with a thickness of 75 μm.

[0060] The second insulating glass layer 35 covers the resistive heating element 40 and the power supply line 42 to insulate and protect them and maintain their sliding characteristics with the fixing belt 20. The electrode 41 is not covered by the second insulating glass layer 35.

[0061] Figure 4 The diagram shows a perspective view of the connector 70 mounted on the heater 22 and the heater retaining component 23. Figure 4 As shown, connector 70 has a resin housing 71 and contact terminals 72 fixed to the housing 71. Contact terminals 72 are leaf springs. Contact terminals 72 include a pair of mating portions 72a that respectively contact the electrodes 41 of heater 22. Contact terminals 72 of connector 70 are connected to a power supply wiring harness 73.

[0062] Connector 70 is mounted on heater 22 and heater holder 23 such that the front and rear sides of heater 22 and heater holder 23 are clamped by connector 70. Thus, each contact portion 72a of contact terminal 72 elastically contacts (presses) electrode 41. As a result, resistive heating element 40 and power supply provided in the image forming apparatus are electrically connected via connector 70, and power can be supplied from the power supply to resistive heating element 40.

[0063] Figure 5 The diagram shown is a schematic diagram of the circuit for supplying power to the heater according to this embodiment.

[0064] like Figure 5 As shown, the AC power supply 200 is electrically connected to the electrode 41 of the heater 22, forming a power supply circuit for supplying power to the resistive heating element 40 in this embodiment.

[0065] In AC power supply 200 and electrode 41 ( Figure 5 A switch 210 is provided between the electrodes 41B. The power supply to the resistive heating element 40 can be switched by turning the switch 210 on and off.

[0066] Controller 220 is based on thermistor 25 (see Figure 2The controller 220 controls the energization of the resistive heating element 40 by detecting the temperature and also taking into account the heat transferred to the sheet during its passage. The controller 220 includes a microcomputer comprising, for example, a central processing unit (CPU), read-only memory (ROM), random access memory (RAM), and input / output (I / O) interfaces. In this embodiment, the controller 220 is disposed within the apparatus body of the image forming apparatus 100. However, in some embodiments, the controller may be disposed within the fixing apparatus.

[0067] Incidentally, in an image forming apparatus including the aforementioned fixing device, electrical problems may occur, leading to abnormal images.

[0068] For example, during the secondary transfer process, when the charged sheet P passes through the fixing clamping section N2, the surface layers of the fixing belt 20 and the pressure roller 21 become charged. Additionally, the surfaces of the fixing belt 20 and the pressure roller 21 become triboelectrically charged due to the rotation of both. When the sheet P passes through the fixing clamping section N2 with the surface layers of the fixing belt 20 and the pressure roller 21 charged, the toner image on the sheet P may experience electrostatic shift, resulting in an abnormal image. This problem is particularly prone to occur in low-humidity environments or when forming images on sheets with high surface resistance due to the coating agent.

[0069] Furthermore, in the fixing device 9 of this embodiment where AC voltage is applied to the heater 22, the insulating layer in the heater 22 and the rubber layer of the fixing belt are equivalent to capacitors. Therefore, in the configuration where the heater 22 and the fixing belt 20 are in physical contact with each other, the AC voltage is applied to the fixing clamping part N2 via the fixing belt 20. Figure 6 As shown, when the sheet P is in contact with both the transfer clamping part N1 and the fixing clamping part N2, the AC voltage is transmitted to the transfer clamping part N1 via the sheet P (see...). Figure 6 (The direction indicated by the arrow in the image). AC voltage affects the transfer electric field and causes periodic unevenness in concentration in the transfer image, i.e., a striped image. In particular, the above problem is prone to occur when the sheet P has low resistance, such as in a high humidity environment or when thin paper is used as the sheet P. The above problem is also prone to occur in areas where the AC power supply is 220V to 240V. The striped image problem is prone to occur when the length of the sheet P in the sheet transport direction is greater than the sheet transport distance L between the transfer clamp N1 (center position) and the fixing clamp N2 (center position). For convenience, Figure 6 The diagram shows a case where the transfer clamping unit N1 and the fixing clamping unit N2 are arranged in a straight line. However, this arrangement is not limited to a straight line, and the path between the transfer clamping unit and the fixing clamping unit may be curved midway. In this case, the sum of the distances the sheet is transported between the two clamping units is defined as the transport distance L. Figure 6 Also shown is a fixing device having a configuration in which the static removal component according to the following embodiment is not provided. The secondary transfer power supply 230 is connected to the secondary transfer roller 13.

[0070] Next, regarding the aforementioned electrical issues, the configuration of the fixing device according to this embodiment will be explained.

[0071] like Figure 6 As shown, starting from the inside of the fixing tape 20, the fixing tape 20 includes a substrate 20a as a conductive layer, an elastic layer 20b, and a release layer 20c. The inner surface of the substrate 20a forms the inner peripheral surface of the fixing tape 20. The outer surface of the release layer 20c forms the outer peripheral surface of the fixing tape 20. From the viewpoint of improving durability and ensuring release properties, the release layer 20c according to this embodiment is a non-conductive layer made of perfluoroalkoxyalkane (PFA). Alternatively, fluoropolymers such as PTFE can also be used as the release layer 20c.

[0072] The release layer 21c of the pressure roller 21 is a conductive layer made of PFA containing a conductive filler such as carbon. The outer surface of the release layer 21c constitutes the outer peripheral surface of the pressure roller 21. The surface resistivity of the outer peripheral surface of the pressure roller 21 is set to 1×10⁻⁶. 8 Below Ω / □. Surface resistivity was measured under the following conditions using a high-resistivity resistivity meter (product name: Hiresta IP [MCP-HT450], manufactured by Mitsubishi Chemical Analytech).

[0073] Probe used: HA type (dual needle type: 20mm spacing)

[0074] Measurement mode: ρs

[0075] Measurement time: 10 seconds

[0076] Applied voltage: 250V

[0077] Measurement locations: a total of 12 locations, including 4 locations in the circumferential direction (90° intervals) and 3 locations in the axial direction (the center and the position 20mm inward from both ends).

[0078] Surface resistivity: average value of 12 locations in total.

[0079] like Figure 7 As shown, an exposed portion 20d is provided at one end of the fixing belt 20 along its long side. The exposed portion 20d is the part of the fixing belt 20 where the elastic layer 20b and the release layer 20c are not provided, and the substrate 20a of the conductive layer is exposed to the outside. The exposed portion 20d is disposed on the outside of the sheet passage area along its long side, and in this embodiment, it is disposed within a range of 5 mm from one end of the fixing belt 20.

[0080] The first electrostatic removal brush 26, serving as an electrostatic removal component, contacts the exposed portion 20d of the fixing belt 20. The second electrostatic removal brush 27, also serving as an electrostatic removal component, contacts the outside of the sheet passage area at one long-side end of the pressure roller 21. In this embodiment, both the first and second electrostatic removal brushes 26 and 27 are made of stainless steel.

[0081] The first brush 26 is grounded through the first resistor 45. The second brush 27 is grounded through the second resistor 46. The resistance value of the first resistor 45 is set to 3 × 10⁻⁶. 6 Below Ω. The second resistor 46 is set at 1.1 × 10 Ω. 3 ~160×10 6 Within the range of Ω.

[0082] In this embodiment, the charge on the surface layers of the fixing belt 20 and the pressure roller 21 is removed by the second de-energizing brush 27 through the surface layer of the pressure roller 21. This configuration can limit the charging of the surface layers of the fixing belt 20 and the pressure roller 21 and prevent electrostatic shift of the toner image on the sheet P during the fixing process.

[0083] In the above configuration, the second brush 27 contacts the surface layer of the pressure roller 21. This is achieved when the sheet P is in contact with both the transfer clamping part N1 and the fixing clamping part N2 (see...). Figure 6 The secondary transfer current can leak from the secondary transfer roller 13 to the ground via the sheet P, the pressure roller 21, and the second de-energizing brush 27. Therefore, the electric field required for the secondary transfer may not be obtained, and secondary transfer failure may occur. This problem is particularly likely to occur in environments with high relative humidity, where the resistance of the sheet P decreases.

[0084] On the other hand, in this embodiment, the second de-energizer 27 is grounded via the second resistor 46, which limits the current flowing to the second de-energizer 27 and limits the leakage of secondary transfer current.

[0085] The higher the resistance value of the second resistor 46, the better it can limit the leakage of secondary transfer current. However, on the other hand, when the resistance value of the second resistor 46 is large, the current removal performance relative to the surface layer of the fixing belt 20 and the pressure roller 21 will decrease. Therefore, it is preferable to set an appropriate resistance value for the second resistor 46 while taking into account the balance between the two.

[0086] Therefore, in this embodiment, the resistance value of the sheet actually used in the image forming apparatus is measured, and the resistance value of the second resistor 46 is set based on the measurement result. Specifically, plain paper copier (PPC) sheets of various brands are placed in an environment of 27°C and 80% RH (relative humidity) for more than 24 hours. Then, the surface resistivity is measured using the HA type probe of the Hiresta IP (MCP-HT450) measuring instrument manufactured by Mitsubishi Chemical Analytech. As a result, the value obtained by applying 100V for 10 seconds is that the sheet has a resistivity of 100 × 10⁻⁶. 6 The lowest resistivity is Ω / □. Therefore, the resistance of 1 mm of sheet in the conveying direction is 1 × 10⁻⁶. 6 Ω / mm. Due to Figure 6 If the length L in the middle is 80mm, the resistance of the paper is 80×10. 6 Ω.

[0087] In this embodiment, considering the aforementioned balance, the resistance value of the second resistor 46 is set within the range of 0.5 to 2 times the resistance value of the paper sheet. That is, preferably, the resistance value of the second resistor 46 is set to be greater than 40 × 10⁻⁶. 6 Ω and less than 160×10 6 Within the range of Ω, specifically, it is set to 100×10 6 Ω. This configuration prevents leakage of secondary transfer current and achieves appropriate static elimination properties relative to the surface layers of the fixing belt 20 and the pressure roller 21.

[0088] Assuming the resistance of each 1 mm of sheet is 1 × 10⁻⁶ 6 If the resistance value R2Ω of the second resistor 46 is Ω / mm and the distance between the transfer clamping part and the fixing clamping part is Lmm, then the resistance value R2Ω of the second resistor 46 can be set to satisfy the following expression (1). This configuration can prevent the leakage of the secondary transfer current toward the second resistor 46 as described above, and ensure the static elimination performance of the surface layer relative to the fixing belt 20 and the pressure roller 21.

[0089] 0.5×L×1×10 6 <R2<2×L×1×10 6 Expression 1

[0090] The resistance value R2Ω of the second resistor 46 can be set according to the following expression (2), where RAΩ / mm represents the resistance value of the sheet per 1mm in the conveying direction. This configuration can prevent leakage of secondary transfer current toward the second resistor 46 and ensure the static elimination performance of the surface layer relative to the fixing belt 20 and the pressure roller 21.

[0091] 0.5 × L × RA < R² < 2 × L × RA (Expression 2)

[0092] Furthermore, in this embodiment, such as Figure 8 As shown, the first de-energizing brush 26 contacts the substrate 20a of the fixing belt 20, which is disposed between the surface layers of the heater 22 and the fixing belt 20. Therefore, a portion of the AC component (50Hz) of the AC power supply 200 transmitted from the resistive heating element 40 of the heater 22 via the fixing belt 20 and the sheet P to the transfer clamping part N1 can escape to the ground side via the first de-energizing brush 26. That is, the above configuration restricts the transmission of AC components from the resistive heating element 40 via the second insulating glass layer 35, the fixing belt 20 (cylindrical substrate 20a, elastic layer 20b, and release layer 20c), and the sheet P to the secondary transfer clamping part N1, and directs the AC components from the resistive heating element 40 via the second insulating glass layer 35, the cylindrical substrate 20a, and the first de-energizing brush 26 to the first de-energizing brush 26 so that the AC components escape to the ground side. Therefore, the appearance of striped images can be prevented.

[0093] As described above, the first de-energizing brush 26 and the second de-energizing brush 27 involved in this embodiment can solve the problem of electricity in the fixing device 9 and the transfer device near the fixing device 9.

[0094] Considering that the capacitive reactance Xc of the second insulating glass layer 35 of heater 22 is 5×10 6 Up to 12×10 6 Ω, the resistance value of the first resistor 45 is preferably set to 3 × 10 Ω. 6 Ω or less. This limits the propagation of AC components to the secondary transfer side. Specifically, in this embodiment, the resistance value of the first resistor 45 is set to 3 × 10⁻⁶. 6 Ω.

[0095] As described above, in this embodiment, the first de-energizing brush 26 and the second de-energizing brush 27 are grounded via different first resistors 45 and second resistors 46, respectively, thus allowing grounding via the required resistance values ​​for each brush. Therefore, the aforementioned electrical problems can be appropriately prevented. In particular, the second resistor 46 needs to have a large resistance value to prevent current leakage from the secondary transfer side. For this purpose, as described above, the resistance value of the second resistor 46 is set to be greater than the resistance value of the first resistor 45. However, the resistance values ​​of the first resistor 45 and the second resistor 46 will vary depending on the sheet transport distance L, the capacitive reactance Xc of the second insulating glass layer 35, etc.

[0096] Furthermore, when the first resistor 45 and the second resistor 46 can be set to the same resistance value, a single brush can contact the fixing belt 20 and the pressure roller 21. That is, as Figure 9 As shown, a single descaling brush 28 can contact the exposed portion 20d of the fixing belt 20 and the outer peripheral surface of the pressure roller 21. The descaling brush 28 is grounded via a resistor 47.

[0097] The above embodiments are illustrative and do not limit the invention. Therefore, it should be understood that, within the scope of the appended claims, many additional modifications and variations can be made to the invention beyond those specifically described herein.

[0098] In the above description, the fixing belt 20 is provided with an exposed portion 20d, in which the substrate 20a, which serves as a conductive layer, is exposed to the outside. The first static-eliminating brush 26 contacts the exposed portion 20d. However, in some embodiments, the exposed portion 20d may not be provided in the fixing belt 20. For example, the static-eliminating component may contact the inner surface of the cylindrical substrate 20a, which serves as the inner surface of the fixing belt 20.

[0099] As in Figure 10 In the fixing device 9 shown, the first de-electrode brush 26 and the second de-electrode brush 27 can be held by a common holding part 29. The holding part 29 is formed of an insulating sheet.

[0100] In the above description, the second insulating glass layer 35 of the heater 22 is in direct contact with the inner surface of the fixing belt 20. However, in some embodiments, another conductive component may be inserted between the second insulating glass layer 35 and the fixing belt 20. For example, such as Figure 11 As shown, the fixing device 9 according to the embodiments of this disclosure includes a heat spreader 50, which is a highly thermally conductive component, between the second insulating glass layer 35 and the fixing belt 20.

[0101] The vapor chamber 50 is a component that contacts the fixing belt 20 from its inner circumferential surface. The vapor chamber 50 is made of a component having a higher thermal conductivity than the substrate 30. In this embodiment, aluminum is used as the material of the vapor chamber 50, and the thermal conductivity of the vapor chamber 50 is set to, for example, approximately 236 W / m·K. Alternatively, SUS (having a thermal conductivity of 16.7 to 20.9 W / m·K) or copper-based materials (having a thermal conductivity of, for example, 381 W / m·K) can be used for the vapor chamber 50.

[0102] Next, the method for calculating thermal conductivity will be explained. To calculate thermal conductivity, the thermal diffusivity of the object under test is first measured. Thermal diffusivity is then used to calculate thermal conductivity.

[0103] Thermal diffusivity was measured using a thermal diffusivity-thermal conductivity measuring device (product name: ai-Phase Mobile 1u, manufactured by ai-Phase Co., Ltd.).

[0104] In order to convert thermal diffusivity into thermal conductivity, values ​​for density and specific heat capacity are required.

[0105] Density was measured using a dry automatic density meter (product name: Accupyc 1330, manufactured by Shimadzu Corporation).

[0106] Specific heat capacity was measured using a differential scanning calorimeter (DSC-60, manufactured by Shimadzu Corporation), with sapphire as the reference material for which specific heat capacity is known. In this embodiment, the specific heat capacity was measured five times, and the average value at 50°C was used. The thermal conductivity λ was obtained by the following expression (3), where ρ is density, C is specific heat capacity, and α is thermal diffusivity obtained by the above-described thermal diffusivity measurement.

[0107] λ=ρ×C×α expression 3

[0108] The heat spreader 50, which contacts the fixing belt 20 along its long side, causes the heat of the fixing belt 20 to move along its long side and become uniform. This configuration can reduce temperature non-uniformity of the fixing belt 20 along its long side.

[0109] Even in such a fixing device, the brushes can be arranged in the same manner as described above, and electrical problems in and around the fixing device can be prevented as in the above embodiments.

[0110] The image forming apparatus involved in the embodiments of this disclosure can be not only as... Figure 1 The color image forming apparatus shown can also be, for example, a monochrome image forming apparatus, a copier, a printer, a fax machine, or a multifunctional peripheral device that includes at least two of the functions of a copier, a printer, and a fax machine.

[0111] For example, Figure 12 The monochrome image forming apparatus 100 shown includes a photoreceptor 110. A charging roller 111, a developing unit 112, a cleaning blade 113, etc., are arranged around the photoreceptor 110. The developing unit 112 includes, for example, a developing roller 115. A transfer unit 116 is arranged across the sheet transport path B, opposite the photoreceptor 110. The position opposite the photoreceptor 110 and the transfer unit 116 is the transfer section C.

[0112] The image forming apparatus 100 also includes an exposure unit 102, a sheet supply unit 103, and a fixing unit 9. The exposure unit 102 includes a mirror 117. The sheet supply unit 103 includes a sheet supply tray 118 and a sheet supply roller 119. The photoreceptor 110, the charging roller 111, the developing unit 112, the transfer unit 116, and the fixing unit 9 constitute an image forming apparatus for forming an image on a sheet.

[0113] Next, refer to Figure 12 The basic operation of the image forming apparatus 100 will be explained.

[0114] At the start of the imaging process, firstly, the charging roller 111 charges the surface of the photoreceptor 110. Then, the exposure apparatus 102 irradiates the photoreceptor 110 with a laser beam Lb based on the image data. The potential decreases at the portion of the photoreceptor 110 irradiated by the laser beam Lb, and an electrostatic latent image is formed at that portion of the photoreceptor 110. The developing apparatus 112 supplies toner to the electrostatic latent image formed on the surface of the photoreceptor 110 to visualize the electrostatic latent image as a toner image, i.e., a developer image. The transfer apparatus 116 transfers the toner image onto the sheet P, and the cleaning blade 113 removes the toner remaining on the surface of the photoreceptor 110.

[0115] On the other hand, when the imaging operation begins, the feed roller 119 of the sheet supply device 103 located at the lower part of the image forming apparatus 100 is driven and rotated to supply the sheet P from the sheet supply tray 118 to the sheet transport path B.

[0116] The alignment roller 120 is controlled to transport the sheet P, which is supplied to the sheet transport path B, to the transfer section C, so that the sheet P faces the toner image on the photoreceptor 110. The transfer device 116 applies a transfer bias to the photoreceptor 110 to transfer the toner image onto the surface of the sheet P that is transported to the transfer section C.

[0117] A sheet P carrying a toner image is conveyed to a fixing unit 9. A heated fixing belt 20 and a pressure roller 21 heat and pressurize the sheet P to fix the toner image onto its surface. The sheet P with the toner image fixed on it separates from the fixing belt 20, is conveyed by a pair of transport rollers located downstream of the fixing unit 9, and discharged to a paper discharge tray. The paper discharge tray is located outside the image forming apparatus 100.

[0118] By applying the configuration of the fixing device 9, including the first de-electrostatic brush 26 and the second de-electrostatic brush 27 (or a single de-electrostatic brush 28), to the image forming apparatus 1 described above, electrical problems in the fixing device 9 and its surroundings (e.g., the transfer section C upstream of the fixing device 9 in the sheet transport direction) are prevented. This configuration can limit the propagation of, for example, AC components of AC power towards the transfer section C. This configuration can also remove charge from the surface layers of the fixing belt 20 and the pressure roller 21. This configuration also prevents the transfer current from leaking from the transfer section C to the pressure roller 21.

[0119] The sheet P used as the recording medium can be thick paper, postcards, envelopes, plain paper, thin paper, coated paper, art paper, tracing paper, OHP (Outer Harmony Projector) transparent film, plastic film, prepreg, copper foil, etc.

[0120] The heating apparatus disclosed herein is not limited to the fixing apparatus described in the above embodiments. The heating apparatus disclosed herein can also be applied, for example, to a dryer for drying ink coated onto sheets, a coating apparatus (lamination apparatus) for heating a covering member used on the surface of a sheet such as paper under pressure, and a heating apparatus such as a heat-sealing machine for sealing the sealing portion of packaging materials using heat and pressure. This prevents electrical problems that may occur in or around the heating apparatus.

[0121] The above embodiments are illustrative and do not limit the invention. Therefore, many additional modifications and variations can be made in view of the above teachings. For example, within the scope of the invention, elements and / or features of different illustrative embodiments can be combined with and / or substituted for each other. In addition, the number, position, shape, etc. of the constituent parts are not limited to this embodiment, but can be any number, position, shape, etc. suitable for implementing the invention.

[0122] This application is based on and claims priority to Japanese Patent Application No. 2021-077673, filed with the Japan Patent Office on April 30, 2021, the entire disclosure of which is incorporated herein by reference.

[0123] List of reference numerals

[0124] 1 Image forming apparatus

[0125] 9. Fixing unit (heating unit)

[0126] 20 Fixing belt (heated rotating body or component)

[0127] 20a substrate (conductive layer)

[0128] 20b Elastic Layer

[0129] 20c release layer

[0130] 21. Pressure belt (pressure rotating body)

[0131] 21c release layer

[0132] 22. Heater (Heating Element)

[0133] 26 First electrostatic eliminator (electrostatic eliminator component)

[0134] 27. Second electrostatic eliminator (electrostatic eliminator component)

[0135] 30 Substrate

[0136] 40 Resistance heating element

[0137] 45 First resistor

[0138] 46 Second resistor

[0139] N1 Fixing Clip (Clipping Section)

[0140] N2 Transfer Clamping Section (Clamping Section or Transfer Section)

[0141] X Long side direction

[0142] Y-direction (short side)

Claims

1. A heating device, comprising: A flat heater having a substrate and a resistive heating element; A heating rotating body that is in contact with the heater and includes a conductive layer; A pressurized rotating body that applies pressure and has an outer surface including a conductive material; as well as One or more current-eliminating components in contact with the conductive layer and the outer surface of the pressurized rotating body. The one or more current-eliminating components include a first current-eliminating component that contacts the conductive layer and a second current-eliminating component that contacts the outer surface of the pressurized rotating body. The first power-eliminating component in contact with the conductive layer is grounded via a first resistor, wherein the second power-eliminating component in contact with the outer surface of the pressurized rotating body is grounded via a second resistor, and wherein the resistance value of the second resistor is greater than the resistance value of the first resistor.

2. The heating device according to claim 1, in, R² was set at 0.5 × L × 1 × 10⁻⁶. 6 <R2<2×L×1×10 6 Within the range of the expression, Here, the transport distance of the recording medium in the transport direction between the fixing clamp and the transfer section upstream of the fixing clamp is L millimeters, the resistance value of the second resistor is R2 ohms, and the resistance value of the recording medium per millimeter in the transport direction is 1×10⁻⁶. 6 Ohms per millimeter.

3. The heating device according to claim 1, in, The one or more current-removing components include conductive brushes.

4. The heating device according to any one of claims 1 to 3, in, The surface resistivity of the outer surface of the pressurized rotating body is 1×10⁻⁶. 8 Ω / □ or smaller.

5. The heating device according to any one of claims 1 to 3, in, The heated rotating body includes an elastic layer.

6. The heating device according to any one of claims 1 to 3, in, The heating device is a fixing device that uses heat to fix an image onto a recording medium.

7. An image forming apparatus, comprising: The heating device according to any one of claims 1 to 6.

Images