Heating device and image forming apparatus

Abstract

To prevent a resistance heating layer or the like from being peeled at a part where a sudden temperature change occurs at the time of heating without adding a new member in a heating roll in which at least an electric insulating layer and the resistance heating layer are provided in this order on one or both of the inner peripheral surface and outer peripheral surface of a metallic cylindrical roll base material where rust may occur.SOLUTION: The heating device includes a heat roll 53A that rotates to heat a member to be heated. In the heat roll 53A, at least an electric insulating layer 532 and a resistance heating layer 533A are provided in this order on one or both of the inner peripheral surface and the outer peripheral surface of a cylindrical roll base material 531 made of metal capable of generating rust without the presence of a rust-proofing layer 535.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a heating device and an image forming apparatus. [Background technology]

[0002] Patent Document 1 describes a heat-generating fixing roll that includes a cylindrical core, an insulating layer laminated inside the core, and a heating element laminated on the insulating layer. Furthermore, Patent Document 1 describes that a metal foil pipe having a larger thermal expansion coefficient than the core metal is inserted into the inner surface of the heating element via another insulating layer. Furthermore, Patent Document 1 also describes that the core metal is preferably made of iron or the like and must be subjected to parker treatment to prevent rust. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2001-134124 A (Claim 1, paragraph 0006, Figure 1) Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention provides a heating device that can prevent peeling of the resistance heating layer, etc., in areas where a sudden temperature change occurs during heating, without adding any new components, in a heating roll in which at least an electrical insulating layer and a resistance heating layer are provided in that order on one or both of the inner and outer peripheral surfaces of a cylindrical roll substrate made of metal that is susceptible to rust, and an image forming apparatus using the same. [Means for solving the problem]

[0005] The first aspect of the present invention is a heating roll that rotates to heat the member to be heated; The heating roll is a heating device in which at least an electrical insulating layer and a resistance heating layer are provided in this order on one or both of the inner and outer peripheral surfaces of a cylindrical roll base made of a metal that can rust, without the presence of a rust-proofing layer.

[0006] The second aspect of the present invention is the heating device of the first aspect, The resistance heating layer is a heating device provided in a divided pattern such that the heat generating regions differ in the axial direction of the heating roll.

[0007] The third aspect of the present invention is the heating device of the second aspect, The divided pattern is a heating device that is divided into patterns corresponding to the difference in width of the heated member along the axial direction of the heating roll.

[0008] A fourth aspect of the present invention is the heating device of the first aspect, The heating device has a heating element disposed in the internal space of the roll substrate, the heating element having a structure in which heat-generating portions are divided into different parts in the axial direction of the heating roll.

[0009] A fifth aspect of the present invention is the heating device of the fourth aspect, The resistance heating layer is a heating device provided as one continuous layer in the axial and circumferential directions of the heating roll.

[0010] A sixth aspect of the present invention is the heating device of the first aspect, In the heating device, a rust-proofing layer is provided on the portion of the roll base where the electrical insulating layer and the resistance heating layer are not provided.

[0011] The seventh aspect of the present invention is The image forming apparatus has a fixing device including a heating device according to any one of the first to sixth means.

[0012] The eighth aspect of the present invention is the image forming apparatus according to the seventh aspect, the fixing device is a fixing device using a fixing belt that is stretched around a plurality of rolls including the heating roll and rotates, The heating roll is a heating roll in the heating device of the image forming apparatus. [Effects of the Invention]

[0013] According to the heating device of the first means described above, in a heating roll in which at least an electrical insulating layer and a resistance heating layer are provided in this order on one or both of the inner and outer peripheral surfaces of a cylindrical roll substrate made of metal that is susceptible to rust, peeling of the resistance heating layer, etc., in areas where a sudden temperature change occurs during heating can be prevented without adding any new components.

[0014] According to the heating device of the second means, the temperature distribution during heating in the axial direction of the heating roll can be adjusted without using a heating element other than the resistance heating layer.

[0015] According to the heating device of the third means, heating can be performed in a way that suppresses the temperature difference that occurs between the parts of the heating roll through which the heated member passes and the parts through which it does not pass, compared to when the divided pattern of the resistance heating layer is not divided to correspond to the difference in width of the heated member.

[0016] According to the heating device of the fourth means, heating can be performed more efficiently to suppress the temperature difference that occurs between the part of the heating roll through which the heated member passes and the part that does not pass, compared to when a heating element with a divided structure is not arranged in the internal space of the roll base.

[0017] According to the heating device of the fifth means, the warm-up time of the heating roll can be shortened compared to when the resistance heating layer is provided in a divided pattern.

[0018] According to the heating device of the sixth aspect, it is possible to prevent problems caused by rusting of the portions of the roll base where the electrical insulating layer and the resistance heating layer are not provided.

[0019] According to the image forming apparatus of the seventh means, it is possible to prevent the resistance heating layer or the like from peeling off in the heating roll of the fixing device in the area where a sudden temperature change occurs during heating, without adding any new components.

[0020] According to the image forming apparatus of the eighth means, wear of the resistance heating layer due to contact with the fixing belt can be prevented compared to when a heating roll in a fixing device is used in which at least an electrical insulating layer and a resistance heating layer are provided in that order on the outer peripheral surface of the roll substrate. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic diagram of an image forming apparatus according to a first embodiment of the present invention. [Figure 2] 1 is a schematic diagram of a fixing device which is an example of a heating device according to Embodiment 1. FIG. [Figure 3] 3 is a schematic diagram showing a partial cross section of a heating roll and the like which are part of the fixing device in FIG. 2. FIG. [Figure 4] 3A is a schematic cross-sectional view of the heating roll of FIG. 2, and FIG. 3B is a schematic cross-sectional view of the heating roll of FIG. 2 taken along line BB. [Figure 5] FIG. 10 is a schematic diagram of a fixing device which is an example of a heating device according to a second embodiment. [Figure 6] 6 is a schematic diagram showing a partial cross section of a heating roll and the like which are part of the fixing device in FIG. 5. [Figure 7] 7A is a schematic cross-sectional view of the heating roll of FIG. 6, and FIG. 7B is a schematic cross-sectional view of the heating roll of FIG. [Figure 8] FIG. 11 is a schematic diagram of a fixing device which is an example of a heating device according to a third embodiment. [Figure 9] FIG. 1A is a schematic cross-sectional view of a heating roll of a comparative example, and FIG. 1B is a schematic cross-sectional view of the heating roll of FIG. 1A taken along line BB. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described.

[0023] Embodiment 1 Fig. 1 shows an image forming apparatus 1 equipped with a heating device 5 according to embodiment 1. Fig. 2 shows a fixing device 5A, which is an example of the heating device 5 according to embodiment 1.

[0024] In this specification and the drawings, substantially the same components are denoted by the same reference numerals, and redundant explanations of the same components will be omitted in this specification. The arrow +X in Figure 1 etc. indicates the right direction when viewed from the front side of the image forming apparatus 1 etc., and the arrow -X indicates the left direction at that time. The arrow +Y in Figure 1 etc. indicates the upward direction of the image forming apparatus 1 etc., and the arrow -Y indicates the downward direction. The symbol +Z in Figure 1 etc. indicates the depth direction when viewed from the front side of the image forming apparatus 1 etc., and the symbol -Z indicates the forward direction at that time. In addition, the symbol "x" inside a "circle" in Figure 1 etc. indicates the direction from the front to the back of the paper of the drawing. The symbol "·" inside a "circle" in Figure 1 etc. indicates the direction from the back to the front of the paper of the drawing.

[0025] (Image forming device) The image forming apparatus 1 is an apparatus that forms an image made of a developer on a sheet-like recording medium 9, which is an example of a heated member. As the sheet-like recording medium 9, for example, a recording paper cut to a predetermined size is used.

[0026] The image forming apparatus 1 has an image forming device 2, a medium supply device 4, a medium transport device 45, a fixing device 5A, etc. arranged in the internal space of a housing 10. In Fig. 1, reference numeral 15 denotes a control device, and reference numeral 17 denotes a power supply device.

[0027] The housing 10 is a structure formed in a predetermined shape. The housing 10 is divided into an upper section and a lower section by, for example, a partition plate 11. The partition plate 11 is provided with a medium passage port 12. In addition, a medium discharge port 13 is provided in a part of the side surface of the housing 10.

[0028] The image forming device 2 is a device that forms a toner image made of toner as a developer and transfers it onto a recording medium 9 . The image forming device 2 is configured as a device that employs an image forming method such as an electrophotographic method.

[0029] The image forming device 2 includes a photosensitive drum 21 and devices such as a charging device 22, an exposure device 23, a developing device 24, a transfer device 25, and a cleaning device 26 arranged around the photosensitive drum 21. The exposure device 23 is a device that exposes the photosensitive drum 21 based on image information input from the outside to form an electrostatic latent image. The image information is information related to the image to be formed, such as characters, figures, photographs, patterns, etc.

[0030] The medium supply device 4 is a device that stores and feeds out the recording medium 9 to be supplied to the transfer position TP in the image forming device 2. The medium supply device 4 is composed of devices such as a container 41 that stores recording media 9 and a delivery device 43 that delivers the recording media 9 one by one. The medium supply device 4 in the first embodiment includes, for example, two containers 41A and 41B. The containers 41A and 41B can store, as the recording media 9, recording media 9A and 9B that are different in size, for example.

[0031] The medium transport device 45 is a device that transports the recording medium 9 to a predetermined position within the housing 10. The dashed dotted lines in FIG. 1 indicate the main transport path when the recording medium 9 is transported within the housing 10 by the medium transport device 45. The medium transport device 45 is made up of a pair of transport rolls 46 (46a to 46f), a guide path member (not shown), and the like. The pair of transport rolls 46 is a pair of transport rolls that sandwich and transport the recording medium 9. The guide path member is a member that forms a transport path, etc. that guides and transports the recording medium 9. The medium transport device 45 has the pair of transport rolls 46, guide path members, etc. arranged in required positions and in required quantities.

[0032] The fixing device 5A is a device that applies heat and pressure to the unfixed toner image transferred by the image forming device 2 to fix it onto the recording medium 9. The fixing device 5A has a fixing housing 50 and includes a heating rotor 51, a pressure rotor 61, and other components arranged in the interior space thereof.

[0033] 2, the fixing housing 50 is a structure provided with an inlet 50a and an outlet 50b for the recording medium 9. The heating rotor 51 is a structure that rotates mainly by applying a heating action. The pressure rotor 61 is a structure that rotates mainly by applying a pressure action. In the fixing device 5A, the heating rotor 51 and the pressure rotor 61 are arranged to rotate in contact with each other. The contacting portion is a fixing processing section FN that performs a fixing process of heating and pressurizing the recording medium 9 and the toner image as they pass through. The fixing device 5A will be described in detail later.

[0034] Next, the operation of the image forming apparatus 1 to form an image will be described.

[0035] In the image forming apparatus 1, a command for an operation of forming an image is received by the control device 15. The control device 15 is a device that controls the operation of each operating unit in the image forming apparatus 1 based on input information, detection information, a control program, etc.

[0036] At this time, in the image forming device 2, the photosensitive drum 21 begins to rotate in the direction of arrow A. In addition, in the image forming device 2, charging, exposing, developing, transferring, and cleaning operations are performed on the rotating drum 21. In addition, the medium supply device 4 performs an operation of supplying the recording medium 9 to the transfer position TP of the image forming device 2 in cooperation with the medium transport device 45. Furthermore, the fixing device 5A is kept in a state where it can perform the fixing operation. The transfer position TP is a position where the photosensitive drum 21 and the transfer device 25 in the image forming device 2 face each other.

[0037] As a result, in the image forming device 2, a toner image corresponding to the image information is formed on the photosensitive drum 21. Meanwhile, in the medium supply device 4, after feeding out a predetermined recording medium 9, it is transported to the transfer position TP via the medium transport device 45. Then, at the transfer position TP of the image forming device 2, the toner image is transferred from the photosensitive drum 21 onto the recording medium 9.

[0038] Subsequently, in the image forming apparatus 1, the recording medium 9 onto which the toner image 92 has been transferred is sent out from the transfer position TP and conveyed to the fixing device 5A.

[0039] At this time, the fixing device 5A introduces the recording medium 9 onto which the toner image 92 has been transferred into the fixing unit FN and passes it through, thereby carrying out the fixing operation by the fixing device 5A. At this time, the temperature in the fixing unit FN is maintained at a predetermined fixing temperature by the heating operation of the heating rotor 51. Then, in the fixing device 5A, the toner image 92 on the recording medium 9 is heated under pressure in the fixing part FN and fixed to the recording medium 9.

[0040] In the image forming apparatus 1, the recording medium 9 after fixing is discharged from the fixing device 5A and transported to the medium discharge port 13 by the medium transport device 45. As a result, the recording medium 9 after fixing is sent from the medium discharge port 13 to a medium accumulation unit (not shown) and accumulated.

[0041] Through the above series of operations, the basic image forming operation for forming a monochromatic image on one side of one sheet of recording medium 9 is completed.

[0042] (heating device: fixing device) Next, the fixing device 5A, which is an example of the heating device 5, will be described in detail.

[0043] 2, the fixing device 5A uses a heating unit 51A in a belt-nip configuration as the heating rotor 51. The fixing device 5A also uses a pressure roll 62 in a roll configuration as the pressure rotor 61.

[0044] The heating unit 51A is a unit including a fixing belt 52, a heating roll 53A, a passing support 54, an adjusting support roll 55, an end connector 56, an external heating element 70, and the like.

[0045] The fixing belt 52 is a belt that contributes to the fixing operation by coming into contact with the surface of the recording medium 9 onto which the toner image 92 has been transferred in the fixing unit FN. The fixing belt 52 is heated by a heating roll 53A.

[0046] The fixing belt 52 is an endless cylindrical member that is flexible, heat-resistant, and thermally conductive. The fixing belt 52 is a laminated belt in which an elastic layer and a release layer are formed in this order on the outer peripheral surface of a cylindrical belt substrate. The belt substrate is a cylindrical member made of a synthetic resin such as polyimide or polyamide, the elastic layer is made of an elastic material such as silicone rubber, and the release layer is made of a resin material such as polytetrafluoroethylene.

[0047] The fixing belt 52 is rotatably wound around a heating roll 53A, a passing support 54, and an adjusting support roll 55. The fixing belt 52 is rotated in the direction indicated by an arrow B in the wound state.

[0048] The heating roll 53A is a roll that heats the fixing belt 52 while rotating in contact with the inner circumferential surface of the fixing belt 52. The heating roll 53A also serves as a roll that indirectly heats the recording medium 9 and the toner image via the fixing belt 52.

[0049] Therefore, the fixing belt 52 is a member to be heated directly by the heating roll 53A, and the recording medium 9 and the toner image are members to be heated indirectly by the heating roll 53A.

[0050] The heating roll 53A is rotatably supported by a unit frame (not shown) via a bearing 538 (see FIG. 3) provided on the end connector 56. The unit frame may be a part of the fixing housing 50 or may be separate from the fixing housing 50 .

[0051] The heating roll 53A has an electric insulating layer 532 and a resistance heating layer 533A provided in this order on the inner circumferential surface of the roll substrate 531. Furthermore, the heating roll 53A has a rust-proofing layer 535 provided on the outer peripheral surface of the roll substrate 531.

[0052] The roll substrate 531 is a cylindrical substrate made of metal that can rust. Rust can occur when the surface of a metal is susceptible to oxidation-reduction reactions with oxygen and moisture in the natural environment, producing corrosive materials. Iron is used as a metal that can rust, but metals such as copper are also applicable. The roll base material 531 is formed as a cylindrical body with a wall thickness of about 0.2 to 1.0 mm.

[0053] The electrical insulating layer 532 is a layer (film) made of an electrically insulating material. The electrical insulating layer 532 is formed on the entire inner circumferential surface of the roll substrate 531 . In particular, the electrical insulating layer 532 is provided directly on the inner peripheral surface of the roll substrate 531 without the rust-proofing layer 535 being present.

[0054] The electrical insulating layer 532 is formed from a material such as polyimide, polyether ether ketone (PEEK), etc. The electrical insulating layer 532 is formed as a layer of a predetermined thickness using the above material by a method such as spray coating or dipping coating. The electrical insulating layer 532 formed on the inner circumferential surface of the roll substrate 531 is formed before rust develops on the inner circumferential surface of the roll substrate 531 .

[0055] The resistance heating layer 533A is a layer that generates heat when current is applied, and can be said to be an internal heating element because the resistance heating layer 533A generates heat within the heating roll 53A itself. The resistance heating layer 533A is formed in an area slightly wider than the maximum width W1 (see FIG. 3) of the recording medium 9 during transport on the inner circumferential surface of the roll substrate 531. The width of the recording medium 9 during transport is the dimension of the portion of the recording medium 9 along the axial direction J (see FIG. 3) of the heating roll 53A. The resistance heating layer 533A is formed as one continuous layer in the axial direction J and the circumferential direction of the heating roll 53A.

[0056] The resistive heating layer 533A is formed as a layer (film) made of a material such as a carbon metal filler mixture, silver palladium, or gold palladium. The resistance heating layer 533A is formed by a method such as spray coating.

[0057] Furthermore, the resistance heating layer 533A is energized via the power supply layer 534 when power is supplied. The power supply layer 534 is provided along the circumferential direction with a predetermined width on both ends in the axial direction J of the inner circumferential surface of the roll substrate 531 (see FIG. 4(B)). The power supply layer 534 is formed as a layer or film made of a material such as beryllium copper or silver paste. A predetermined amount of electricity is supplied to the power supply layer 534 from a power supply contact 57, which will be described later.

[0058] The rust-proofing layer 535 is a treatment layer for preventing the surface of the roll substrate 531 from rusting. The rust-proofing layer 535 is provided on the outer peripheral surface of the roll substrate 531 .

[0059] Strictly speaking, the rust-proofing layer 535 is also formed on the following portions of the roll substrate 531. That is, it is also formed on portions of the roll substrate 531 where neither the electrical insulating layer 532 nor the resistance heating layer 533A is provided. These portions where neither is provided are, for example, the end faces on both ends of the roll substrate 531. By forming the rust-proofing layer on these portions as well, problems caused by rust on the above-mentioned portions of the roll substrate 531 where neither is provided are prevented.

[0060] Furthermore, the anti-rust treatment layer 535 may be a layer formed of a treatment agent (anti-rust agent) that prevents the occurrence of rust. The anti-rust treatment layer 535 is formed, for example, by adopting a method such as chemical conversion treatment using a treatment agent such as zinc phosphate. Here, the rust prevention layer 535 in the first embodiment does not need to be provided on the inner peripheral surface of the roll substrate 531 .

[0061] The following methods can be adopted to avoid providing the rust-proofing layer 535 on the inner circumferential surface of the roll substrate 531, for example. These methods include not providing the rust-proofing layer from the beginning, or removing the rust-proofing layer after providing it on the inner circumferential surface of the roll substrate 531. When removing the rust-proofing layer once provided, it can be removed by washing with an acidic solution or the like.

[0062] The end connectors 56 are attached to and held at both ends of the heating roll 53A. The end connector 56 is made of a short cylindrical frame with a through hole in the center, and is made of a non-conductive material. The end connectors 56 are fixed by fitting both ends of the heating roll 53A into the internal space of the cylindrical frame, so that the end connectors 56 are attached to both ends of the heating roll 53A.

[0063] As shown in FIG. 3, the end connector 56 has a bearing 538 disposed on the outer peripheral surface of the cylindrical frame. As a result, the end connector 56 is rotatably attached to a unit frame (not shown) via the bearing 538 together with the heating roll 53A.

[0064] As shown in FIG. 3, the heating roll 53A has contact power feeders 57 disposed inside both ends of the roll substrate 531.

[0065] The contact power feeder 57 is a structure that contacts the power feed layer 534 of the heating roll 53A to feed power. As a result, the contact power feeder 57 feeds power to the resistance heating layer 533A via the power feed layer 534.

[0066] The contact power feeder 57 may be, for example, a structure in which a plurality of rotary terminals 572 are rotatably attached to an annular frame 571. The contact power feeder 57 is attached to a unit frame (not shown) or rotatably supported by the end connector 56.

[0067] Furthermore, contact power feeder 57 is connected to power supply device 17 as shown in Fig. 3. The dashed dotted lines in Fig. 3 indicate the electrical wiring. When the time comes when heating is required, the contact power feeder 57 receives a predetermined current or the like from the power supply device 17 and supplies power.

[0068] The passing support 54 is a structure that supports the fixing belt 52 so that it passes through the fixing processing section FN. The passing support 54 is composed of a support body 541, a pad member 542, etc. The support body 541 is a rigid member in the shape of a square tube that is arranged to extend parallel to the axial direction J of the heating roll 53A. The pad member 542 is a flexible member that is attached to the surface of the support body 541 on the side that comes into contact with the inner circumferential surface of the fixing belt 52. In addition, the passage support 54 has both longitudinal ends of the support body 541 attached and fixed to a unit frame (not shown).

[0069] The adjusting support roll 55 is a roll that applies tension to the fixing belt 52 and adjusts and supports the fixing belt 52 so as to stabilize the state of rotation and running. The adjusting support roll 55 is also called a steering roll that displaces so as to suppress the occurrence of meandering of the fixing belt 52. The adjustment support roll 55 is rotatably and displaceably attached to a unit frame (not shown) so as to contact and support the inner circumferential surface of the fixing belt 52. The shaft of the adjustment support roll 55 is biased in a predetermined direction by a biasing member (not shown) such as a spring.

[0070] Next, the external heating element 70 is a heating element that is disposed in the internal space of the roll substrate 531 and generates heat by itself to heat the heating roll 53A. The external heating element 70 is a heating element separate from the heating roll 53A, and is therefore an external heating element.

[0071] 3, the external heating element 70 in the first embodiment is made up of a first external heating element 70A and a second external heating element 70B. Furthermore, as the external heating element 70, for example, a halogen lamp (heater) is used.

[0072] The first external heating element 70A and the second external heating element 70B are divided so that the heat generating portions 71 are different in the axial direction J of the heating roll 53A. That is, the first external heating element 70A has a heat-generating portion 71 disposed in a central portion Ha, which is a region toward the center in the axial direction J. The second external heating element 70B has a heat-generating portion 71 disposed in end portions Hb and Hc, which are regions located outside both ends of the central portion Ha.

[0073] The central portion Ha is a zone of a width that is set based on the width W2 of the small size group, which has a relatively narrow width W during transport of the recording medium 9. Specifically, the width W2 is the maximum width within the small size group. The end portions Hb and Hc are the areas on both sides that remain when the central portion Ha is subtracted from the maximum width W1 of the recording medium 9 during transport. The end portions Hb and Hc are also areas with widths set based on the width W1 of the large size group, which has a relatively wide width W of the recording medium 9. The width W1 is the maximum width within the large size group. The width of the recording media 9 included in the large size group is wider than the width W2 but less than or equal to the width W1.

[0074] Incidentally, the center Ha and end Hb, Hc at this time are the positions set when transporting using the center registration method, which is a method for transporting the recording medium 9 so that the center of the width W is aligned with the center reference of the width of the transport path.

[0075] The first external heating element 70A and the second external heating element 70B are attached at their respective ends to a unit frame or the like (not shown). 3, the first external heating element 70A and the second external heating element 70B are individually connected to the power supply unit 17. Therefore, either or both of the first external heating element 70A and the second external heating element 70B can generate heat by switching between energizing and de-energizing. The switching between energizing the first external heating element 70A and the second external heating element 70B is controlled by the control unit 15.

[0076] As shown in FIG. 2, the heating unit 51A is provided with a lubricant application device 58 and a temperature sensor 59. The lubricant applicator 58 is a device that applies a lubricant to the inner circumferential surface of the fixing belt 52. The temperature sensor 59 is a sensor that measures the surface temperature of the heating roll 53A. Of these, the temperature sensor 59 includes a plurality of temperature sensors 59a to 59c arranged at three positions in the axial direction J of the heating roll 53A (see FIG. 3).

[0077] Furthermore, in heating unit 51A, detection (measurement) information obtained by temperature sensors 59a to 59c is transmitted to control device 15. Meanwhile, control device 15 controls the power supply operation of power supply device 17 in accordance with the detection information. As a result, the heating unit 51A adjusts the heating state of the heating roll 53A while detecting the surface temperature of the heating roll 53A.

[0078] Next, as shown in Fig. 2, the pressure roll 62 is a roll body having a structure in which an elastic release layer 622 is provided on the outer peripheral surface of a roll substrate 621. Reference numeral 623 in Fig. 2 etc. denotes a shaft portion.

[0079] The roll substrate 621 has a shape including a columnar or cylindrical main body and shafts at both ends of the main body. The pressure roll 62 is supported by a pressure support mechanism (not shown) that is arranged inside the fixing housing 50 .

[0080] The pressure support mechanism rotatably supports the shaft 623 of the pressure roll 62 via a bearing. The pressure support mechanism supports the shaft 623 of the pressure roll 62 so that the main body of the pressure roll 62 is pressed against the fixing belt 52 in the fixing processing unit FN. The pressure support mechanism urges the shaft 623 of the pressure roll 62 with a predetermined pressure using an urging member such as a spring. As a result, the pressure roll 62 presses the fixing belt 52 passing through the fixing processing section FN against the passing support 54 with a predetermined pressure. The pressure support mechanism can also move the pressure roll 62 to a position away from the fixing process section FN (passage support 54).

[0081] Furthermore, a passive gear (not shown) is disposed at least at one end of the pressure roll 62. The passive gear is in mesh with a transmission gear that transmits rotational power from a rotation drive device (not shown). As a result, when the time comes to operate the pressure roll 62, the driven gear receives rotational power and the pressure roll 62 is driven to rotate in the direction of arrow C.

[0082] (heating operation or fixing operation) The fixing device 5A operates as follows.

[0083] In the fixing device 5A, when the main power supply of the image forming apparatus 1 is turned on, the heating roll 53A is heated in the heating unit 51A. Also, in the fixing device 5A, the pressure roll 62 starts to rotate.

[0084] At this time, the pressure roll 62 receives rotational power from a rotation drive device (not shown) and starts to rotate in the direction of arrow C. As a result, in the fixing device 5A, the fixing belt 52 receives rotational power from the pressure roll 62 in the fixing part FN and is rotated in the direction of the arrow B.

[0085] At this time, power is supplied from the power supply device 17 to the resistance heating layer 533A and the external heating element 70 of the heating roll 53A. Power is supplied to the resistance heating layer 533A from the power supply device 17 via the contact power feeder 57 and the power feed layer. Power is also supplied to the external heating element 70 from the power supply device 17 to the first external heating element 70A and the second external heating element 70B.

[0086] As a result, in the fixing device 5A, the roll substrate 531 of the heating roll 53A is heated by the heat generated by the resistance heating layer 533A and the heat generated by the external heating element 70. Also, in the fixing device 5A, the fixing belt 52 is heated by the heating roll 53A and maintained in a heated state up to a predetermined fixing temperature.

[0087] In this case, the fixing device 5A has a heating roll 53A made of an iron roll base 531, and is heated by both a resistance heating layer 533A and an external heating element . Therefore, in the fixing device 5A, the warm-up time of the heating roll 53A and therefore the fixing belt 52 can be shortened.

[0088] When the fixing belt 52 is heated to a predetermined fixing temperature, the fixing device 5A is ready to perform the fixing operation.

[0089] Furthermore, in the fixing device 5A, when the image forming operation is performed, the heat generation operation of the external heat generating element 70 is controlled in accordance with the width W of the recording medium 9. At this time, the heat generation operation of the resistance heat layer 533A of the fixing device 5A is stopped.

[0090] That is, when a recording medium 9A having a width included in the large size group is used as the recording medium 9, both the first external heating element 70A and the second external heating element 70B of the external heating element 70 generate heat.

[0091] As a result, the heating roll 53A and the fixing belt 52 are heated in their entirety, from the center portion Ha to the ends Hb and Hc. As a result, in the fixing unit FN, the recording medium 9A having a width included in the large size group is sufficiently heated in the axial direction J.

[0092] On the other hand, when a recording medium 9B having a width included in the small size group is used as the recording medium 9, the first external heating element 70A of the external heating element 70 generates heat. In other words, in this case, the second external heating element 70B does not generate heat.

[0093] As a result, only the central portion Ha of the heating roll 53A and the fixing belt 52 is heated. As a result, in the fixing unit FN, recording media 9B with widths included in the small size group are sufficiently heated in the axial direction J. At the same time, in the fixing unit FN, portions (non-passing portions) through which the recording media 9B do not pass are not heated. The non-passing portions correspond to the ends Hb and Hc. Therefore, the fixing unit FN or the heating roll 53A is prevented from having its ends Hb and Hc absorb heat from the recording medium 9B, and an abnormal rise in temperature can be avoided.

[0094] (If a sudden temperature rise occurs) In the fixing device 5A, when fixing operations are successively performed using the recording medium 9B having a width included in the small size group, for example, the following occurs. In this case, in the fixing device 5A, a sudden temperature change occurs between the center Ha and the ends Hb and Hc of the heating roll 53A.

[0095] The sudden temperature change at this time is thought to be caused by the following factors. That is, the center portion Ha of the heating roll 53A continues to be heated by the first external heating element 70A, accumulating heat and tending to rise in temperature. In contrast, the ends Hb and Hc of the heating roll 53A continue to be unheated by the second external heating element 70B. As a result, the temperature difference between the center portion Ha and the ends Hb and Hc gradually increases.

[0096] In the fixing device 5A, even if a sudden temperature change occurs between the center Ha and the ends Hb and Hc of the heating roll 53A, the following results are obtained. That is, the resistive heating layer 533A and the electrical insulating layer 532 on the inner circumferential surface side in the portion of the heating roll 53A where the temperature rises suddenly do not peel off from the roll substrate 531.

[0097] Therefore, in the fixing device 5A, heating failures of the heating roll 53A and the like and fixing failures caused by peeling of the resistance heating layer 533A and the like are prevented. As a result, in the image forming apparatus 1, the occurrence of poor image quality due to the above-mentioned fixing failure in the fixing device 5A is also prevented.

[0098] (Comparative Examples and Reference Examples) However, when the fixing device 5A employs the heating roll 53X of the comparative example shown in FIG. 9 instead of the heating roll 53A, the following problem occurs. The heating roll 53X of the comparative example is formed by providing an anticorrosive layer 535X on the inner circumferential surface of the roll substrate 531, followed by an electrical insulating layer 532 and a resistance heating layer 533A. Except for the change in providing the anticorrosive layer 535X, the heating roll 53X has the same configuration as the heating roll 53A.

[0099] In the fixing device 5A in which the comparative heating roll 53X was used, when a sudden temperature change occurred between the center Ha and the ends Hb and Hc of the heating roll 53X, the following peeling occurred. In this case, in the fixing device 5A, in the area where the temperature of the heating roll 53X has risen sharply, a part of the resistance heating layer 533A and the electrical insulating layer 532 on the inner peripheral surface side peel off from the roll substrate 531. It is presumed that this peeling is caused by a difference in thermal expansion coefficient between the rust-proofing layer 535X and the electrical insulating layer 532 or the resistance heating layer 533A. Therefore, in this case, in the fixing device 5A, heating failure and fixing failure of the heating roll 53X and the like due to the peeling occur.

[0100] The inventors of the present invention also conducted an evaluation test in which the heating roll 53X' of the reference example was used instead of the heating roll 53X of the comparative example. The heating roll 53X' of the reference example is a heating roll in which the rust-proofing treatment layer 535X is changed to a rust-proofing agent with high heat resistance. The rust-proofing treatment layer 535X of the heating roll 53X' of the reference example is formed by changing the rust-proofing treatment agent, such as zinc phosphate, to have higher heat resistance.

[0101] In the fixing device 5A when the heating roll 53X' of the reference example is applied, when a sudden temperature change occurs between the center Ha and the ends Hb and Hc of the heating roll 53X', the following peeling occurs. In this case, in the fixing device 5A, a part of the resistance heating layer 533A and the electrical insulating layer 532 on the inner circumferential surface side in the part of the heating roll 53X' where the temperature rose suddenly peeled off a little. The degree of peeling at this time was smaller than that when the heating roll 53X of the comparative example was used. However, it was confirmed that even when the heating roll 53X' of the reference example was used, the occurrence of peeling could not be prevented.

[0102] In this regard, in the fixing device 5A according to the first embodiment, even if a sudden temperature change occurs between the center Ha and the ends Hb, Hc of the heating roll 53A, the resistance heating layer 533A and the like do not peel off. Furthermore, in the fixing device 5A, peeling of the resistance heating layer 533A and the like can be prevented without adding a new member such as inserting a metal foil pipe as described in Patent Document 1.

[0103] (additional configuration) In the fixing device 5A according to the first embodiment, if there is a risk of the above-mentioned sudden temperature change occurring, the resistance heating layer 533A may be made to generate heat temporarily during the process. If there is a risk of the above, the second external heating element 70B of the external heating element 70 may be temporarily made to generate heat during the heating.

[0104] A case where the above-mentioned sudden temperature change may occur may be assumed, for example, when a predetermined number of recording media 9B have passed through continuous fixing operations using heat generated only by the first external heating element 70A. The temporary heat generation may be for a period long enough to prevent the sudden temperature change. For example, the temporary heat generation may be for the period of time it takes for a predetermined number of recording media 9B to pass by.

[0105] Embodiment 2 FIG. 5 shows a fixing device 5B according to a second embodiment of the present invention.

[0106] Compared to the fixing device 5A according to the first embodiment (see FIG. 2 etc.), the fixing device 5B has a heating unit 51B that uses a heating roll 53B instead of the heating roll 53A, but otherwise has the same configuration. Heating roll 53B differs from heating roll 53A in the first embodiment in that external heating element 70 is not employed, but is replaced with a resistance heating layer 533B (see FIGS. 5 and 6).

[0107] The resistance heating layer 533B of the heating roll 53B is provided in a divided pattern so that the heat generating regions differ in the axial direction J of the heating roll 53B. That is, as shown in FIG. 7(B), the resistive heating layer 533B is divided into a first resistive heating layer 533B1, a second resistive heating layer 533B2, and a third resistive heating layer 533B3.

[0108] The first resistive heating layer 533B1 is a resistive heating layer portion that heats the center portion Ha in the axial direction J. The second resistive heating layer 533B2 and the third resistive heating layer 533B3 are resistive heating layer portions that heat the end portions Hb and Hc in the axial direction J, respectively. The central portion Ha and the end portions Hb, Hc are areas defined by the same criteria as the central portion Ha and end portions Hb, Hc described in the first embodiment.

[0109] The first resistive heating layer 533B1, the second resistive heating layer 533B2 and the third resistive heating layer 533B3 are formed using the same material as the resistive heating layer 533A in the first embodiment. The boundaries between the first resistive heating layer 533B1 and the second and third resistive heating layers 533B2 and 533B3 are formed as follows: The boundaries are formed as gaps where none of the resistive heating layers are provided, or as areas where an electrical insulating layer is provided.

[0110] As shown in FIG. 6, the resistance heating layer 533B is supplied with power by three pairs of contact power feeders 57a, 57b, and 57c. The contact power feeder 57a supplies power by contacting both ends of the first resistance heating layer 533B1 via a pair of contact power feeders 57a1 and 57a2. The contact power feeder 57b supplies power by contacting both ends of the second resistance heating layer 533B2 via a pair of contact power feeders 57b1 and 57b2. The contact power feeder 57c contacts both ends of the third resistive heating layer 533B3 via a pair of contact power feeders 57c1 and 57c2 to feed power.

[0111] The three pairs of contact power feeders 57a, 57b, and 57c are each attached to a unit frame or the like (not shown). As shown in Fig. 6, the three pairs of contact power feeders 57a, 57b, and 57c are each connected to a power supply device 17. The dashed dotted lines in Fig. 6 indicate the electrical wiring. When the time comes for heating to be required, the contact power feeders 57a, 57b, and 57c are supplied with a predetermined current or the like from the power supply device 17 to feed power.

[0112] Therefore, the first resistive heating layer 533B1, the second resistive heating layer 533B2, and the third resistive heating layer 533B3 can generate heat in part or in whole by switching between energizing and de-energizing. Furthermore, switching between energizing the first resistive heating layer 533B1, the second resistive heating layer 533B2, and the third resistive heating layer 533B3 is controlled by the control device 15.

[0113] (heating operation, fixing operation) In the fixing device 5B, when an image forming operation is performed, the heat generation operation of the resistance heating layer 533B is controlled in accordance with the width W of the recording medium 9.

[0114] That is, when a recording medium 9A having a width included in the large size group is used as the recording medium 9, the following heating operation is performed. In this case, the first resistive heating layer 533B1, the second resistive heating layer 533B2 and the third resistive heating layer 533B3 all perform heat generation operations.

[0115] When the recording medium 9B having a width included in the small size group is used as the recording medium 9, the following heating operation is performed. In this case, only the first resistive heating layer 533B1 generates heat, and the second resistive heating layer 533B2 and the third resistive heating layer 533B3 do not generate heat.

[0116] Incidentally, with the heating roll 53B, it is possible to adjust the temperature distribution in the axial direction J during heating without using the external heating element 70 in the first embodiment in combination.

[0117] In the fixing device 5B, for example, when fixing operations using the recording medium 9B having a width included in the small size group are performed consecutively, the following occurs. In this case, in the fixing device 5B, a sudden temperature change occurs between the center Ha and the ends Hb and Hc of the heating roll 53B.

[0118] The sudden temperature change at this time is thought to be caused by the following factors. That is, the center Ha of the heating roll 53B continues to be heated by the first resistance heating layer 533B1, accumulating heat and tending to increase in temperature, whereas the ends Hb and Hc of the heating roll 53B continue to be unheated by the second resistance heating layer 533B2 and the third resistance heating layer 533B3. As a result, the temperature difference between the central portion Ha and the ends Hb and Hc gradually increases.

[0119] In the fixing device 5B, even if a sudden temperature change occurs between the center Ha and the ends Hb and Hc of the heating roll 53B, the following results are obtained. That is, the resistive heating layer 533B and the electrical insulating layer 532 on the inner circumferential surface side in the portion of the heating roll 53B where the temperature rises suddenly do not peel off from the roll substrate 531.

[0120] Therefore, in the fixing device 5B, heating failures of the heating roll 53B and the like and fixing failures caused by peeling of the resistance heating layer 533B and the like are prevented. As a result, in the image forming apparatus 1, the occurrence of poor image quality due to the above-mentioned fixing failure in the fixing device 5B is also prevented.

[0121] (additional configuration) In the fixing device 5B, if there is a risk of the above-mentioned sudden temperature change occurring, in addition to the first resistive heating layer 533B1, the second resistive heating layer 533B2 and the third resistive heating layer 533B3 may also be temporarily heated during the process.

[0122] Embodiment 3 FIG. 8 shows a fixing device 5C according to a third embodiment of the present invention.

[0123] Compared to the fixing device 5A according to the first embodiment (see FIG. 2 etc.), the fixing device 5C has a heating unit 51C instead of the heating unit 51A as the heating rotator 51. Other than this, the fixing device 5C has the same configuration. The heating unit 51C is not a belt-nip type heating unit, but a roll type heating unit that uses a heating roll 53C.

[0124] The heating unit 51C includes a heating roll 53C, an external heating element 70, and the like. In this case, the heating roll 53C is a roll that directly heats the recording medium 9 or the toner image.

[0125] The heating roll 53C is configured in almost the same manner as the heating roll 53A in the first embodiment, except for some differences such as the outer diameter of the roll. The heating roll 53C has an end connector 56 (see FIG. 3) similar to the heating roll 53A in the first embodiment. Similarly to the external heating element 70 in the first embodiment, the external heating element 70 in the heating roll 53C is made up of a first external heating element 70A and a second external heating element 70B. Furthermore, the heating roll 53C is driven to rotate in the direction of arrow B.

[0126] In the fixing device 5C, the portion where the heating roll 53C and the pressure roll 62 come into contact with each other is the fixing processing portion FN. In the fixing device 5C, the recording medium 9 onto which the toner image 92 has been transferred is introduced into a fixing unit FN and passed through the fixing unit FN, where the fixing operation is performed.

[0127] The fixing device 5C operates in substantially the same manner as the fixing device 5A according to the first embodiment.

[0128] Also, in the fixing device 5C, for example, when fixing operations using recording media 9B having a width included in the small size group are performed consecutively, the following occurs. In this case, a sudden temperature change occurs between the center Ha and the ends Hb and Hc of the heating roll 53C (see FIG. 3).

[0129] In the fixing device 5C, even if the above-mentioned sudden temperature change occurs in the heating roll 53C, the next peeling does not occur. That is, the resistive heating layer 533A and the electrical insulating layer 532 (see FIG. 4) on the inner circumferential surface side of the heating roll 53C in the area where the temperature rises suddenly do not peel off from the roll substrate 531.

[0130] Therefore, in the fixing device 5C, heating failures of the heating roll 53C and the like and fixing failures caused by peeling of the resistance heating layer 533A and the like are prevented. As a result, in the image forming apparatus 1, the occurrence of poor image quality due to the above-mentioned fixing failure in the fixing device 5C is also prevented.

[0131] (Modification of the third embodiment) In the fixing device 5C, the heating roll 53B in the second embodiment may be applied in place of the heating roll 53C in the heating unit 51C. Heating roll 53B in this modification differs from heating roll 53A in embodiment 1 in the following respects: In other words, heating roll 53B in the modification does not employ external heating element 70, but instead employs a resistance heating layer 533B.

[0132] Variant. The present invention is not limited to the configuration examples exemplified in the above embodiments. In other words, the present invention can be modified as necessary as long as the gist of the invention described as a means for solving the problem is not changed. Therefore, the present invention also includes the following modifications, for example.

[0133] The heating device 5 of the present invention may be, for example, a device that heats a member to be heated that requires heating and drying. In this case, the heating device 5 heats the member to be heated by conveying it so that it comes into direct or indirect contact with the heating roll. The member to be heated in this case may be any member that can be dried by direct or indirect contact with the heating roll.

[0134] The resistance heating layers 533A, 533B, etc. of the heating roll in the heating device 5 may be provided on the outer circumferential surface of the roll substrate 531. The resistance heating layers 533A and 533B may be provided on both the inner and outer peripheral surfaces of the roll substrate 531. When the resistance heating layers 533A and 533B are provided on both the inner and outer peripheral surfaces of the roll substrate 531, the rust prevention treatment layer is not provided on either the inner or outer peripheral surface.

[0135] Furthermore, the heating roll in the heating device 5 may have layers other than the rust-proofing layer 535 on the inner or outer peripheral surface of the roll substrate 531 on which the resistance heating layers 533A and 533B are provided. Furthermore, the resistance heating layer 533B and the external heating element 70 in the heating device 5 may be configured in a pattern in which the regions or portions to be heated are divided into a number other than three. Furthermore, the configuration of the rotation drive system of the heating rotor 51 and the pressurizing rotor 61 in the heating device 5 may be configured differently from the configuration exemplified in the first embodiment.

[0136] In the first embodiment and the like, the image forming apparatus 1 that forms a monochrome image has been exemplified as the image forming apparatus 1. However, the image forming apparatus 1 of the present invention may be of another type as long as it requires a fixing device including the heating device 5. For example, the image forming apparatus 1 of the present invention may be an apparatus that forms a multi-color image by combining toners of multiple colors using an intermediate transfer method or the like.

[0137] (Addendum) (((1))) a heating roll that rotates to heat the member to be heated; The heating roll is a heating device in which at least an electrical insulating layer and a resistance heating layer are provided in this order on one or both of the inner and outer peripheral surfaces of a cylindrical roll base made of a metal that can rust, without the presence of a rust-proofing layer. (((2))) The heating device according to (((1))), wherein the resistance heating layer is provided in a divided pattern such that heat-generating regions differ in the axial direction of the heating roll. (((3))) The heating device according to (((2))), wherein the divided pattern is a pattern divided in accordance with a difference in width of the heated member along the axial direction of the heating roll. (((4))) The heating device according to (((1))), wherein a heating element having a structure in which heat-generating portions are divided into different parts in the axial direction of the heating roll is disposed in the internal space of the roll substrate. (((5))) The heating device according to (((4))), wherein the resistance heating layer is provided as a single continuous layer in the axial and circumferential directions of the heating roll. (((6))) The heating device according to (((1))), wherein an anti-rust treatment layer is provided on a portion of the roll base where the electrical insulating layer and the resistance heating layer are not provided. (((7))) An image forming apparatus having a fixing device including the heating device according to any one of (((1))) to (((6))). (((8))) the fixing device is a fixing device using a fixing belt that is stretched around a plurality of rolls including the heating roll and rotates, The image forming apparatus according to ((7)), wherein the heating roll is a heating roll in the heating device.

[0138] According to the heating device of (((1))), in a heating roll in which at least an electrical insulating layer and a resistance heating layer are provided in this order on one or both of the inner and outer peripheral surfaces of a cylindrical roll base made of metal that is susceptible to rust, peeling of the resistance heating layer, etc., in areas where a sudden temperature change occurs during heating can be prevented without adding any new components. According to the heating device of (((2))), the temperature distribution during heating in the axial direction of the heating roll can be adjusted without using a heating element other than the resistance heating layer. According to the heating device of (((3))), heating can be performed which suppresses the temperature difference that occurs between the part of the heating roll through which the heated member passes and the part through which the heated member does not pass, compared to when the divided pattern of the resistance heating layer is not divided in accordance with the difference in width of the heated member. According to the heating device of (((4))), heating can be performed more efficiently to suppress the temperature difference that occurs between the part of the heating roll through which the heated member passes and the part that does not pass, compared to when a heating element with a divided structure is not arranged in the internal space of the roll base. According to the heating device of (((5))), the warm-up time of the heating roll can be shortened compared to when the resistance heating layer is provided in a divided pattern. According to the heating device of (((6))), it is possible to prevent problems caused by rusting of the portions of the roll base where the electrical insulating layer and the resistance heating layer are not provided. According to the image forming device of (((7))), it is possible to prevent the resistance heating layer or the like from peeling off in the heating roll of the fixing device in the area where a sudden temperature change occurs during heating, without adding any new components. According to the image forming apparatus of (((8))), it is possible to prevent wear of the resistance heating layer due to contact with the fixing belt, compared to when a heating roll in a fixing device is used in which at least an electrical insulating layer and a resistance heating layer are provided in this order on the outer peripheral surface of the roll substrate. [Explanation of symbols]

[0139] 1...Image forming device 5...Heating device 5A, 5B, 5C...fixing device (an example of a heating device) 9...Recording medium (an example of a heated member) 9A...Recording media with widths included in the large size group 9B...Recording media with widths included in the small size group 52...Fuser belt 53A, 53B, 53C...heating rolls 70...External heating element 70A...First external heating element 70B...Second external heating element 71...heat-generating part 531...Roll substrate 532...Electrical insulating layer 533A... Resistance heating layer (an example of a resistance heating layer consisting of one continuous layer) 533B... Resistance heating layer (an example of a resistance heating layer with divided heat generating areas) 535...Rust prevention layer J…Axis direction Ha: Center (an example of a heat generating area) Hb, Hc...edges (examples of heat generating areas) W: Width along the axial direction

Claims

1. a heating roll that rotates to heat the member to be heated; The heating roll is a heating device in which at least an electrical insulating layer and a resistance heating layer are provided in this order on one or both of the inner and outer peripheral surfaces of a cylindrical roll base made of a metal that can rust, without the presence of a rust-proofing layer.

2. 2. The heating device according to claim 1, wherein the resistance heating layer is provided in a divided pattern such that heat generating regions differ in the axial direction of the heating roll.

3. 3. The heating device according to claim 2, wherein the divided patterns correspond to differences in width of the heated member along the axial direction of the heating roll.

4. 2. The heating device according to claim 1, wherein a heating element having a structure in which heat generating portions are divided into different parts in the axial direction of the heating roll is disposed in the internal space of the roll substrate.

5. 5. The heating device according to claim 4, wherein the resistance heating layer is provided as a single continuous layer in the axial and circumferential directions of the heating roll.

6. 2. The heating device according to claim 1, wherein an anticorrosive layer is provided on a portion of the roll base where the electrical insulating layer and the resistance heating layer are not provided.

7. An image forming apparatus having a fixing device including the heating device according to claim 1 .

8. the fixing device is a fixing device using a fixing belt that is stretched around a plurality of rolls including the heating roll and rotates, 8. The image forming apparatus according to claim 7, wherein the heating roll is a heating roll in the heating device.

Images