JP2015200731A - heating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a heater 234 disposed in a pressure roller 231 from coming into contact with the pressure roller 231 even when a bearing 245 supporting the pressure roller 231 is broken.SOLUTION: A roller restriction part 241a is disposed in a position off a bearing 245 of a pressure roller 231 in such a direction that the pressure roller 231 can move if the bearing 245 is broken. In a state where the bearing 245 is not broken, a space C between positions of the pressure roller 231 and the heater 234 closest to each other and a space E between the pressure roller 231 and the roller restriction part 241a satisfy C>E. Thus, even if the bearing 245 is broken to cause the pressure roller 231 to come off, the pressure roller 231 is brought into contact with the roller restriction part 241a to have the position restricted, so that the heater 234 can be prevented from coming into contact with the pressure roller 231.

Description

  The present invention relates to a heating device such as a fixing device that fixes a toner image onto a recording material by heating the recording material on which the toner image is formed.

  Among image forming apparatuses such as copiers, printers, facsimiles, and multifunction machines having a plurality of these functions, a structure using an electrophotographic method records a toner image through charging, exposure, development, and transfer processes. Form on the material. Then, the toner image is fixed on the recording material by heating with a fixing device. As such a fixing device, a structure in which a heating source such as a halogen heater is provided in a roller constituting the fixing device is conventionally known (see, for example, Patent Document 1).

JP 2004-341346 A

  In the case of a structure in which a heat source is provided in the roller as described above, the end of the roller is rotatably supported by a bearing with respect to a support portion such as a side plate, and the heat source is supported on the support portion separately from the roller. keeping. Here, the fixing device may be used in a state where the bearing is damaged due to careless handling during assembly, the usage period may exceed the expected allowable period, or foreign matter may enter the bearing. In such a case, the bearing may be damaged. When the bearing is broken, the holding height (position) of the roller may be changed by dropping the steel balls, which are a plurality of rolling elements arranged between the inner ring and the outer ring. When the position of the roller changes, there is a possibility that the heating source disposed inside the roller and held separately from the roller contacts the inner peripheral surface of the roller, and this heating source is damaged.

  In view of such circumstances, the present invention was invented to prevent the heating source from coming into contact with the roller even when the bearing supporting the roller is damaged.

  The present invention relates to a roller, a heating source disposed in the roller, a bearing that rotatably supports the roller with respect to a support portion, and the heating source that is held separately from the roller with respect to the support portion. And a roller restricting portion that is disposed in a direction in which the roller can move when the bearing is broken at a position that is disengaged from the bearing of the roller, and that restricts the movement of the roller. In a state where the bearing is not damaged, C> E is satisfied, where C is a gap at a position where the roller and the heating source are closest to each other, and E is a gap between the roller and the roller restricting portion. The heating device is characterized.

  According to the present invention, even if the bearing is broken, the position of the roller is regulated by the roller regulating unit, so that the heating source can be prevented from coming into contact with the roller.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. 1 is a schematic cross-sectional view of a fixing device according to a first embodiment. FIG. 3 is a side view illustrating a configuration for performing belt shift control of the fixing device according to the first embodiment. The figure seen from the G direction of FIG. 6 is a flowchart of belt shift control of the fixing device according to the first embodiment. FIG. 3 is a side view illustrating a belt driving configuration of the fixing device according to the first embodiment. FIG. 3 is a perspective view of a pressure belt unit of the fixing device according to the first embodiment. FIG. 6 is a cross-sectional view of the fixing roller according to the comparative example on the pressure roller end side. Sectional drawing by the side of a pressure roller which shows the state to which the bearing was damaged with the fixing device which concerns on a comparative example. FIG. 3 is a cross-sectional view of the pressure roller end portion side of the fixing device according to the first embodiment. FIG. 3 is a cross-sectional view of the pressure roller end portion side showing a state in which the bearing is damaged in the fixing device according to the first embodiment. FIG. 3 is a diagram illustrating a current detection circuit of the fixing motor according to the first embodiment. 6 is a flowchart for determining contact between a roller and a roller restricting portion according to the first embodiment. FIG. 6 is a partial side view of the fixing device showing another first example of the roller restricting portion according to the first embodiment. FIG. 6 is a partial side view of the fixing device showing a range in which a roller restricting portion is provided in another first example. FIG. 9 is a partial side view of the fixing device showing another second example of the roller restricting portion according to the first embodiment. FIG. 6 is a cross-sectional view of a fixing roller according to a second embodiment of the present invention on the pressure roller end side. Sectional drawing by the side of a pressure roller which shows the state which the bearing damaged in the fixing device which concerns on 2nd Embodiment. The flowchart for determining contact | abutting with the roller which concerns on 2nd Embodiment, and a roller control part. FIG. 6 is a cross-sectional view of a fixing roller according to a third embodiment of the present invention on the pressure roller end side. Sectional drawing by the side of a pressure roller which shows the state which the bearing damaged in the fixing device which concerns on 3rd Embodiment.

<First Embodiment>
A first embodiment of the present invention will be described with reference to FIGS. First, a schematic configuration of the image forming apparatus of the present embodiment will be described with reference to FIG. Note that the image forming apparatus of this embodiment can be applied to a copying machine, a printer, a facsimile machine, a multifunction machine having a plurality of these functions, and the like.

[Image forming apparatus]
The image forming apparatus 100 forms a toner image on a recording material (sheet, sheet material such as an OHP sheet) by an electrophotographic method. The image forming apparatus 100 according to the present embodiment includes, for example, image forming units 200Y, 200M, 200C, and 200K that form four color toner images of Y (yellow), M (magenta), C (cyan), and K (black), respectively. Prepare. These image forming units 200Y, 200M, 200C, and 200K are arranged in series along the traveling direction (rotating direction) of the intermediate transfer belt 25, and the process until the visible image is formed is processed in parallel for each color. Is adopted. Since the basic configurations of the image forming units 200Y, 200M, 200C, and 200K are the same, the subscripts indicating the configuration of the image forming units of the respective colors are omitted unless necessary. explain.

  The surface of the photosensitive drum 20 as an image carrier is uniformly charged to a required potential by a primary charger 21, and then the surface of the photosensitive drum 20 is exposed by an exposure device 22, thereby electrostatically charging the surface of the photosensitive drum 20. A latent image is formed. The electrostatic latent image on the photosensitive drum 20 is developed using a developer by the developing device 23, and is visualized as a toner image. The toner image developed on the photosensitive drum 20 developed by the developing device 23 is transferred onto an intermediate transfer belt 25 which is an endless belt as an intermediate transfer member by a primary transfer device 24. At this time, the toner images of the respective colors are sequentially superimposed and primarily transferred onto the intermediate transfer belt 25.

  Then, the toner image on the intermediate transfer belt 25 on which the primary transfer of all colors has been performed is collectively transferred onto the recording material S by the secondary transfer device 26. The recording material S is conveyed from the cassette 30 to the secondary transfer device 26 by the feeding device 31. After the secondary transfer, the recording material S carrying an unfixed toner image is conveyed to the fixing device 27. The unfixed toner image is melted and softened by being heated and pressed by the fixing device 27 and fixed on the recording material. The recording material S on which the toner image is fixed is discharged to the discharge tray 28. Alternatively, when an image is formed on the back side, the recording material having a toner image fixed on one side is reversed by the reversing path 29 and then conveyed again to the secondary transfer device 26 via the duplex conveying path 32. A toner image is formed on the back side by the same process as described above.

  As described above, a series of image forming processes from charging, exposure, development, transfer, and fixing are executed, and an image is recorded and formed on the recording material S. In the above description, the full-color image forming apparatus has been described. However, in a monochrome image forming apparatus, only a black image forming unit exists. In addition, the arrangement order and the configuration of the image forming units of Y, M, C, and K are not limited to this.

[Fixing device]
Next, a schematic configuration of the fixing device 27 which is a heating device of the present embodiment will be described with reference to FIG. The fixing device 27 includes a fixing belt unit 220A having a fixing belt 220, a pressure belt unit 230A having a pressure belt 230, a fixing motor 240, and the like. Each of the fixing belt 220 and the pressure belt 230 is stretched around two rollers, and the fixing belt 220 and the pressure belt 230 come into contact with each other to form a fixing nip portion. . Then, when the recording material on which the toner image is formed passes through the fixing nip portion, the toner image is fixed on the recording material as described above. The fixing belt unit 220A and the pressure belt unit 230A are configured by the following members.

[Fixing belt unit]
The fixing belt unit 220A includes a fixing belt 220, an induction heating coil 224, and the like. The fixing belt 220 is formed in an endless shape, and the fixing belt 220 is stretched between the fixing roller 221 and the fixing tension roller 222 and rotates (circulates). An induction heating coil 224 is disposed around the fixing belt 220. The fixing belt 220 can be appropriately selected as long as it generates heat by the induction heating coil 224 and has heat resistance. For example, a magnetic metal layer such as a nickel metal layer or a stainless steel layer having a thickness of 100 μm, a width of 380 mm, and a circumferential length of 200 mm coated with silicon rubber having a thickness of 500 μm and a surface layer coated with a PFA tube can be used.

  When an alternating current is passed through the induction heating coil 224, magnetic lines of force are generated around the coil, and an eddy current is generated in the metal layer of the fixing belt 220. This current is changed to Joule heat by the resistance of the metal layer to heat the metal layer, and the fixing belt 220 is heated. A temperature detection means (for example, a thermistor) (not shown) is disposed inside the fixing belt 220, and detects the temperature of the inner surface of the fixing belt 220 based on an output signal of the thermistor. The heating control is set so that the temperature of the inner surface of the fixing belt 220 is 180 ° C., for example.

  The fixing roller 221 is formed, for example, by integrally forming a heat-resistant silicone rubber elastic layer on a core metal surface layer in which an outer diameter of a stainless steel solid material is formed to φ19 mm. The fixing roller 221 is disposed on the recording material outlet side in the fixing nip region between the fixing belt 220 and the pressure belt 230, and the elastic layer of the surface rubber is elastically deformed by pressure contact with the pressure roller 231 described later. And is distorted. The fixing tension roller 222 applies a tension set to 120 N, for example, so as to always maintain the belt tension optimally. The fixing tension roller 222 is a hollow roller formed of, for example, a stainless material and having an outer diameter of about 20 mm and an inner diameter of about 16 mm.

  In addition, the fixing pad stay 223 is arranged inside the fixing belt 220 on the recording material entrance side of the fixing nip portion region between the pressure belt 230 and the fixing belt 220, that is, on the upstream side in the rotation direction of the fixing belt 220 of the fixing roller 221. Is provided. The fixing pad stay 223 is made of, for example, a stainless material. The fixing pad stay 223 is urged toward a pressure pad 233, which will be described later, at a set pressure 400N, for example. Similarly, the fixing roller 221 is urged toward the pressure roller 231 with a set pressure 350N. As a result, the above-described fixing nip portion is formed.

[Pressure belt unit]
On the other hand, the pressure belt unit 230A includes the pressure belt 230, the heater 234, and the like. The pressure belt 230 is formed in an endless shape, and the pressure belt 230 is stretched between both the pressure roller 231 and the pressure tension roller 232 to rotate (circulate). The pressure roller 231 is a hollow roller made of stainless steel (SUS), for example, and has an outer diameter of about 21 mm and an inner diameter of about 19 mm. Has been placed. The pressure tension roller 232 is a hollow roller having an outer diameter of approximately 22 mm and an inner diameter of approximately 20 mm made of, for example, a stainless material, and functions as a roller that applies an appropriate tension to the pressure belt 230.

  A heater 234 as a heating source is disposed inside the pressure roller 231 so as to heat the pressure belt 230. Therefore, in the present embodiment, the fixing belt 220 is heated by an induction heating method using IH, and the pressure belt 230 is supplementarily heated by a heater to cope with high-speed image formation.

  Outside the image area (area through which the recording material passes) on the outer peripheral surface of the pressure belt 230, a temperature detecting means (for example, a thermistor) (not shown) is in contact. Based on the output signal of the thermistor, the temperature of the outer peripheral surface of the pressure belt 230 is detected. For example, the heating control is set so that the surface temperature of the pressure belt becomes 100 ° C.

  The pressure pad 233 is located on the inlet side in the fixing nip region formed between the pressure belt 230 and the fixing belt 220, that is, on the upstream side of the pressure roller 230 in the rotation direction of the pressure belt 230. It is provided inside the corresponding pressure belt 230. The pressure pad 233 is made of, for example, silicon rubber. The pressure pad 233 is pressed against the pressure belt 230 with a set pressure of 400 N, for example, and forms the above-described nip portion together with the pressure roller 231.

[Belt offset control]
Next, the shift control of the fixing belt 220 and the pressure belt 230 will be described with reference to FIGS. The rotation from the fixing motor 240 as a drive source is transmitted to the fixing roller gear 226 fixed to the rotating shaft of the fixing roller 221 so that the fixing roller 221 rotates in the direction of arrow A in FIG. Then, the rotation of the fixing roller 221 is transmitted to the fixing belt 220, and the fixing belt 220 rotates in the arrow B direction. The fixing belt 220 stretched around the two rollers, that is, the fixing roller 221 and the fixing tension roller 222, meanders in the front-rear direction shown in the left-right direction in FIG. 4 due to the misalignment of the rollers.

  The tension spring 300 a applies tension to the fixing belt 220 via a bearing 301 a that supports the end portion of the fixing tension roller 222. The belt tension is, for example, 100N. By applying tension to the belt, the belt is wound around the fixing tension roller 222, and the belt can be displaced by roller steering operation.

  A tensioner 302a is further engaged with the bearing 301a on the outside. The tensioner 302a is engaged with the rotation shaft of the fixing roller 221 and the rotation shaft of the fixing tension roller 222, and can be rotated around the fixing roller 221. One end of the tensioner 302a is provided with gear teeth 303a. The worm gear 304a engaged with the gear teeth 303a is rotated by the motor 310a, so that the tensioner 302a rotates around the fixing roller 221. By this operation, the end of the fixing tension roller 222 can be moved in the direction of arrow C in FIG.

  When the end of the fixing tension roller 222 moves in any direction of the arrow C in FIG. 3, the parallelism between the fixing roller 221 and the fixing tension roller 222 is lost, and the fixing belt 220 is offset. The home position sensor 307a is a photo interrupter, and a home position flag 308a engaged with the tensioner 302a can pass between the light emitting unit and the light receiving unit. Then, when the home position flag 308a is positioned between the light emitting unit and the light receiving unit, the light from the light emitting unit is blocked, and when the home position flag 308a is detached from this time, the light from the light emitting unit is received by the light receiving unit. Is detected. The CPU 400 serving as a control unit can detect the position of the fixing tension roller 222 depending on whether the home position sensor 307a is in a transmission or light shielding state. The CPU 400 may be provided in the fixing device 27, but in the present embodiment, the CPU 400 is provided on the apparatus main body side of the image forming apparatus 100 and controls the entire apparatus.

  As shown in FIG. 4, belt position detection sensors 305 a and 306 a are disposed near both ends of the fixing belt 220. When the fixing belt 220 approaches the front side of FIG. 4, the belt position detection sensor 306a detects the deviation of the belt. Then, the CPU 400 operates the motor 310a to move the fixing tension roller 222 downward in FIG. By this operation, the fixing belt 220 is shifted to the back side in FIG. When the fixing belt 220 moves to the back side, the belt position detection sensor 305a detects the deviation of the belt. Then, the CPU 400 operates the motor 310a to move the fixing tension roller 222 upward in FIG. By this operation, the fixing belt 220 is shifted to the front side in FIG. By repeating the above operation, the fixing belt 220 rotates while reciprocating within a predetermined range. Such fixing belt shift control is performed so as to reciprocate in a range of about 2 mm, for example.

  An example of the flow of the deviation control of the fixing belt 220 will be described with reference to FIG. First, when either one of the belt position detection sensors 305a and 306a detects the deviation of the belt (S1), a steering operation is performed to move the end of the fixing tension roller 222 in any of the directions indicated by the arrow C in FIG. 3 (S2). ). That is, when the belt position detection sensor 305a detects the end of the fixing belt 220 (when 305a is detected), the home position sensor 307a steers in a direction (307a detection direction) in which the home position flag 308a is in a light shielding state. On the other hand, when the belt position detection sensor 306a detects the end of the fixing belt 220 (when 306a is detected), steering is performed in a direction in which the home position sensor 307a enters a transmissive state (307a retracting direction). When the fixing belt 220 moves away from either one of the belt position detection sensors 305a and 306a that have detected the end of the fixing belt 220 (when the belt shift detection position is passed), that is, when the logic of this sensor changes. (Y of S3), it returns to S1. If the sensor logic does not change (N in S3) and a predetermined time (30 seconds) elapses from the detection (Y in S4), a cross-off error is detected (S5), and the operation of the image forming apparatus 100 is stopped and the operation screen is displayed. Inform the user by display or alarm.

  Such belt shift control is similarly performed for the pressure belt 230. That is, as shown in FIGS. 3 and 4, the same configuration as the various sensors used for the deviation control of the fixing belt 220 is used for the pressure belt 230. Therefore, in the above description, the pressure belt 230 is similarly described by replacing the suffixes of the reference numerals of the components from a to b.

[Fixing device drive configuration]
Next, the driving configuration of the fixing device 27 will be described with reference to FIGS. 3, 4, and 6. As described above, the rotation of the fixing motor 240 is transmitted to the fixing roller 221 via the fixing roller gear 226. Here, as shown in FIGS. 3 and 4, the fixing roller gear 226 is fixed to one end portion of the fixing roller 221, and the other end portion (the back side in FIG. 4) of the fixing roller 221 is shown in FIG. As shown, another fixing roller gear 227 is fixed. Accordingly, the rotation of the fixing motor 240 is transmitted to another fixing roller gear 227 via the fixing roller gear 226 and the fixing roller 221. Thus, the rotation transmitted to the other fixing roller gear 227 is transmitted to the idler gear 236 in the pressure belt unit 230A through the fixing idler gear 228 in the fixing belt unit 220A. Then, the rotation is finally transmitted from the idler gear 236 to the pressure roller gear 235 fixed to the end of the pressure roller 231. As a result, the pressure roller 231 is rotated by the fixing motor 240 and the pressure belt 230 is rotated. By setting the number of teeth of these idler gears, the pressure roller 231 rotates at a surface speed of about 5% with respect to the fixing roller 221. Further, the pressure belt unit 230A is axially engaged with a frame of the fixing device 27 (not shown) with respect to the rotation center 237.

[Detailed configuration of pressure belt unit]
Next, the detailed configuration of the pressure belt unit 230A will be described with reference to FIGS. As shown in FIGS. 6 and 7, the pressure belt unit 230 </ b> A includes a pad pressure arm 241 and a roller pressure arm 242. The pad pressure arm 241 holds the pressure pad 233 and presses the pressure pad 233 against the fixing pad stay 223 by a pad pressure spring 243. The roller pressure arm 242 holds the pressure roller 231 and presses the pressure roller 231 against the fixing roller 221 by a roller pressure spring 244 as a first urging unit. A contact pressure is applied between the pressure belt 230 and the fixing belt 220 as a rotating body via the pressure roller 231. The pad pressure spring 243 and the roller pressure spring 244 are respectively disposed between the unit frame 247 of the pressure belt unit 230A, the pad pressure arm 241 and the roller pressure arm 242.

  The unit frame 247 is axially engaged with the frame of the fixing device 27 (not shown) with respect to the rotation center 237, and supports the entire pressure belt unit 230A so as to be rotatable with respect to the rotation center 237. Yes. The unit frame 247 can be moved toward and away from the fixing belt unit 220A by a cam mechanism (contact / separation mechanism) provided with a cam 238, and the pressure belt 230 is driven by driving the cam mechanism. Can be brought into contact with and separated from the fixing belt 220.

  The pad pressure arm 241 and the roller pressure arm 242 are attached toward the fixing belt unit 220A by different springs (pad pressure spring 243 and roller pressure spring 244) arranged between the unit frame 247. It is energized. As described above, the urging force (set pressure) of these springs is 400 N for the pad pressure spring 243 and 350 N for the roller pressure spring 244.

  As shown in FIG. 3, the pressure tension roller 232 that applies tension to the pressure belt 230 is urged by a tension spring 300b as a second urging means. That is, the tension spring 300 b applies tension to the pressure belt 230 via a bearing that supports the end of the pressure tension roller 232. The belt tension is, for example, 100N.

  Both ends of the pressure roller 231 are rotatably supported by the roller pressure arm 242 by bearings (bearings) 245. As shown in FIGS. 8 and 10, the bearing 245 is a radial ball bearing, and serves as a plurality of rolling elements provided in an freely rotatable manner between the inner ring 245a, the outer ring 245b, and the inner ring 245a and the outer ring 245b. And steel balls 245c. In such a bearing 245, a plurality of steel balls 245c roll between the inner ring 245a and the outer ring 245b, whereby the friction coefficient when the inner ring 245a and the outer ring 245b rotate relative to each other, that is, the shaft is rotated. Keep the torque small. Here, the outer ring 245 b is fixed to the roller pressure arm 242, and the inner ring 245 a is fixed closer to the axial end of the pressure roller 231. For this reason, the pressure roller 231 is rotatable with respect to the roller pressure arm 242.

  Further, as described above, the heater 234 is disposed inside the pressure roller 231. In this embodiment, as the heater 234, a halogen lamp (halogen heater) in which a glass tube is filled with a halogen gas and tungsten as a heating element that generates heat when energized is provided in the glass tube is used. The heater may be, for example, a carbon heater using carbon as the heating element as long as the heating element is configured to generate heat when energized in the glass tube. The heater 234 heats the pressure roller 231 with a power setting of 300 W, for example. A heater guide 246 as a holding portion for holding the heater 234 is provided at the end of the pressure roller 231 outside the bearing 245 in the longitudinal direction (rotational axis direction). The heater guide 246 holds the glass portions at both ends of the heater 234. Connector portions at both ends of the heater 234 are connected to connector terminals provided on the unit frame 247. The heater guide 246 is supported by the unit frame 247. In the present embodiment, the unit frame 247, the pad pressure arm 241 and the roller pressure arm 242 constitute a support portion. Therefore, the heater 234 is supported by the heater guide 246 separately from the pressure roller 231 with respect to the support portion. The opposite side of the pressure roller 231 in the longitudinal direction has the same configuration.

[Bearing damage]
Next, a case where the bearing 245 supporting the pressure roller 231 is damaged as described above will be described. If the bearing 245 used for a collision due to handling or greatly exceeds the set life is damaged, the steel ball 245c held between the inner ring 245a and the outer ring 245b may fall off. When the steel ball 245c is dropped, the pressure roller 231 supported by the bearing 245 is also dropped from the normal position.

  Here, the structure of the comparative example shown in FIGS. 8 and 9 will be described. First, in a state where the bearing is not damaged, that is, in a state where the bearing 245 has a plurality of steel balls 245c, the gap at the position where the pressure roller 231 and the heater 234 are closest is C, and the inner ring 245a and the outer ring 245b are Let D be the gap at the closest position. This gap D corresponds to the maximum dropout amount of the pressure roller 231 when the bearing 245 is damaged and the steel ball 245c is dropped. In this case, when the dropout amount D due to breakage of the bearing 245 is larger than the gap C between the pressure roller 231 and the heater 234, the heater 234 and the pressure roller 231 collide as shown in FIG. 234 may also be damaged at the same time. In particular, as in the present embodiment, when the heater 234 has a configuration such as a halogen heater in which a heating element is provided in the glass tube, the glass tube is likely to be damaged by the collision with the pressure roller 231. In FIG. 9, in order to clarify the state, a part of the pressure roller 231 overlaps with the heater 234 indicated by hatching.

[Roller restriction section]
For this reason, in this embodiment, as shown in FIGS. 10 and 11, a roller restricting portion 241a is provided to prevent the heater 234 and the pressure roller 231 from colliding even if the bearing 245 is damaged. . The roller restricting portion 241a is disposed so as to face the peripheral surface of the pressure roller 231 that is removed from the bearing 245, and restricts the movement of the pressure roller 231. In other words, the roller restricting portion 241a is disposed at a position away from the bearing 245 of the pressure roller 231 in a direction in which the pressure roller 231 can move when the bearing 245 is damaged. When 231 falls off, the movement is restricted. In the present embodiment, the roller restricting portion 241a is formed on a part of the pad pressure arm 241. However, the roller restricting portion 241a may be formed on other portions constituting the support portion such as the roller pressure arm 242 and the unit frame 247. .

  This will be specifically described. A part of the pad pressure arm 241 is disposed on the inner side in the longitudinal direction of the pressure roller 231 (closer to the center in the axial direction) than the bearing 245. The shape of the pad pressure arm 241 near the pressure roller 231 is such that the pressure roller 231 escapes. A surface of the pad pressing arm 241 that faces the pressing roller 231 at the escape portion is a roller restricting portion 241a. The roller restricting portion 241 a is a portion where the arm contact portion 231 a that is a part of the peripheral surface of the pressure roller 231 comes into contact when the pressure roller 231 falls off due to breakage of the bearing 245. The clearance E between the roller restricting portion 241a and the arm contact portion 231a is smaller than the clearance C at the position where the pressure roller 231 and the heater 234 are closest to each other (C> E). Further, since the roller restricting portion 241 a is disposed closer to the center in the axial direction of the pressure roller 231 than the bearing 245, the end portion side of the pressure roller 231 can be supported by the bearing 245.

  Further, the gap E is smaller than the gap D at the position where the inner ring 245a and the outer ring 245b are closest to each other (D> E). For this reason, as shown in FIG. 11, when the pressure roller 231 drops due to damage to the bearing 245, the inner ring 245a and the outer ring 245b do not come into contact with each other, and the arm contact portion 231a of the pressure roller 231 serves as a roller restricting portion. 241a abuts. Therefore, even when the steel ball 245c falls off due to breakage of the bearing 245, the maximum dropout amount of the pressure roller 231 is the gap E described above. Since the gap E is smaller than the gap C between the pressure roller 231 and the heater 234, the pressure roller 231 and the heater 234 can be prevented from colliding even if the pressure roller 231 falls off due to damage to the bearing 245.

  Here, if the gap C between the pressure roller 231 and the heater 234 is larger than the gap D between the inner ring 245a and the outer ring 245b, the pressure roller 231 and the heater 234 do not collide even if the steel ball 245c falls off. However, when the gap C is increased, it is necessary to increase the pressure roller 231 and its surrounding parts, and the fixing device 27 is increased in size. For this reason, in the present embodiment, the gap C is smaller than the gap D (D> C). In summary, in the present embodiment, the relationship between the gaps is D> C> E. Such roller restricting portions 241a are preferably provided on both sides of the pressure roller 231 in the axial direction.

[Contact detection]
Next, a configuration for detecting that the arm contact portion 231a of the pressure roller 231 is in contact with the roller restricting portion 241a as described above will be described with reference to FIGS. In the present embodiment, such contact detection determination is performed by detecting the driving torque of the fixing motor 240. Specifically, the current value supplied to rotate the fixing motor 240 at a predetermined rotational speed is detected. This is because the larger the driving torque, the larger the input power to the fixing motor 240 for rotating at a predetermined speed. For this reason, in this embodiment, as shown in FIG. 12, a current detection unit 401 as a contact detection unit and a torque detection unit is provided. The current detection unit 401 detects a current value applied to the fixing motor 240. Since the current value detected by the current detection unit 401 is an analog value, the signal detected by the current detection unit 401 is converted into a digital signal by the A / D converter 402 and input to the CPU 400 as a control unit. .

  The determination flow for contact detection will be described with reference to FIG. First, the CPU 400 checks the current value of the current detection unit 401 as needed (S11), and determines whether the current value exceeds a predetermined current value (S12). When the current value exceeds a predetermined current value, the driving of the fixing motor 240 is stopped as a torque up error. In the present embodiment, the operation of the image forming apparatus 100 is stopped. At this time, the user may be notified by an operation screen or an alarm.

  This will be specifically described. It is assumed that the roller restricting portion 241a and the arm contact portion 231a of the pressure roller 231 come into contact with each other due to damage to the bearing 245. Then, the pressure roller 231 rotates while sliding with the roller restricting portion 241a. As described above, since the pressure roller 231 is pressurized at 350 N by the roller pressure spring 244, the pressure roller 231 rotates while receiving the pressure received by the bearing 245 by the roller restricting portion 241a. For this reason, the driving torque of the fixing motor 240 becomes larger than that before the bearing 245 is damaged. That is, the current value supplied to the fixing motor 240 increases. For this reason, as shown in FIG. 13, when the current value at this time exceeds a predetermined current value that has been set, the CPU 400 determines that the torque is increased, and stops the operation of the image forming apparatus. In other words, the CPU 400 detects that the pressure roller 231 has come into contact with the roller restricting portion 241a when the current value detected by the current detecting portion 401 exceeds a predetermined current value. The predetermined current value is a value that is increased with some margin from the normal current value applied to the fixing motor 240 to rotate the pressure roller 231 and the like in a state where the bearing 245 is not damaged. . For example, it is preferable that the value set as a normal current value is set to 1.2 times, 1.5 times, or the like so that erroneous detection is less likely to occur.

  In the case of this embodiment, even when the bearing 245 is damaged and the pressure roller 231 falls off, the pressure roller 231 comes into contact with the roller restricting portion 241a and its position is restricted, so that the heater 234 is added. Contact with the pressure roller 231 can be prevented. As a result, the heater 234 can be prevented from being damaged. Further, at this time, it is found that the bearing 245 is damaged because the pressure roller 231 is in contact with the roller restricting portion 241a by detecting the driving torque of the fixing motor 240. In this case, since the CPU 240 stops driving the fixing motor 240, it is possible to prevent parts such as gears from being damaged due to the damage of the bearing 245.

  In this embodiment, the driving torque of the fixing motor 240 is detected by detecting the current value applied to the fixing motor 240. For example, a torque sensor is provided on the rotation shaft of the fixing motor 240. Alternatively, the driving torque may be directly detected. In this case, the CPU 400 stops driving the fixing motor 240 when the value detected by the torque sensor as the torque detector exceeds a predetermined threshold.

[Another first example of the roller regulating portion]
Next, another first example of the roller restricting portion described above will be described with reference to FIGS. 14 and 15. In this example, when the bearing 245 is damaged and the pressure roller 231 moves as shown in FIG. 11 described above, the position of the roller restricting portion 241b with which the pressure roller 231 comes into contact is defined, and the roller restricting portion The shape of 241b is devised. That is, in this example, as shown in FIG. 14, the surface of the roller restricting portion 241b that faces the pressure roller 231 has an uneven shape. Thereby, when the pressure roller 231 and the roller restricting portion 241b come into contact with each other when the bearing 245 is damaged, the required driving torque of the fixing motor 240 can be greatly improved. As a result, an increase in the input power of the fixing motor 240 can be easily detected by the current detection unit 401 (FIG. 12), and breakage of the bearing 245 can be detected more easily.

  In the case of this example, the bearing 245 that supports the pressure roller 231 has an urging force of a roller pressure spring 244 as the first urging means as shown in FIGS. The urging force of the tension spring 300b as such second urging means acts. That is, the pressure roller 231 is urged toward the fixing belt 220 by the roller pressure spring 244 via the roller pressure arm 242 and the bearing 245 to form the above-described fixing nip portion. The pressure tension roller 232 that stretches the pressure belt 230 together with the pressure roller 231 is urged by the tension spring 300b to apply tension to the pressure belt 230. For this reason, the bearing 245 is subjected to a pressing force for forming the fixing nip portion by the roller pressing spring 244 and a tension for belt tension by the tension spring 300b. For this reason, when the bearing 245 is damaged, the pressure roller 231 causes the force acting on the pressure roller 231 by the urging force of the roller pressure spring 244 and the force acting on the pressure roller 231 by the urging force of the tension spring 300b. Will move in the direction of the resultant force.

  Therefore, in this example, as shown in FIG. 15, the roller restricting portion 241 b is partially provided not on the entire periphery of the pressure roller 231 but on a part facing the pressure roller 231. In other words, in this example, the roller restricting portion 241b is a resultant force of force F1 acting on the pressure roller 231 by at least the urging force of the roller pressure spring 244 and force F2 acting on the pressure roller 231 by the urging force of the tension spring 300b. Arranged in the direction of F3. Specifically, the resultant force F3 is a position at an angle α (12 ° in this example) with respect to the direction of the force F1. Then, the surface in a predetermined range (less than 1/2 of the circumferential length of the pressure roller 231, for example, about 1/6 to 1/4) along the peripheral surface of the pressure roller 231 around this position. Is in an uneven shape.

  If the driving torque of the fixing motor 240 can be greatly improved when the pressure roller 231 comes into contact with the surface of the roller restricting portion, the friction coefficient is increased by, for example, roughening the surface or devising the material. Other configurations may be used. For example, in the present embodiment, the roller restricting portion is made of metal such as stainless steel, but the roller restricting portion itself may be made of a material having a large friction coefficient such as rubber.

[Another second example of the roller regulating portion]
Next, another second example of the roller restricting portion described above will be described with reference to FIG. In this example, in order to increase the friction coefficient of the surface of the roller restricting portion 241c facing the pressure roller 231, a friction material 241e having a friction coefficient larger than this surface is provided on the surface of the base portion 241d. That is, the roller restricting portion 241c is provided with a base portion 241d formed of a metal such as stainless steel, and a friction material 241e made of silicon rubber as a friction material on the surface of the base portion 241d facing the pressure roller by bonding or the like. When the bearing 245 is damaged and the pressure roller 231 falls off, the pressure roller 231 comes into contact with the friction material 241e. Thereby, when the pressure roller 231 comes into contact with the roller restricting portion 241c, the driving torque of the fixing motor 240 is greatly increased, and the breakage of the bearing 245 is easily detected. The friction material 241e may be a member having a large friction coefficient such as rubber other than silicon rubber or felt.

<Second Embodiment>
A second embodiment of the present invention will be described with reference to FIGS. In the first embodiment described above, the contact of the pressure roller 231 with the roller restricting portion 241a is detected by detecting the current value applied to the fixing motor 240. On the other hand, in the present embodiment, such contact detection is detected by the temperature detected by the thermistor 250 as a temperature detection unit that detects the surface temperature of the pressure roller 231. Since other configurations and operations are the same as those of the first embodiment described above, overlapping illustrations and descriptions are omitted or simplified, and the same reference numerals are given to equivalent configurations, and hereinafter the first embodiment. It demonstrates centering on a different part.

  In the present embodiment, the thermistor 250 is disposed in the vicinity of the pressure roller 231. Specifically, the thermistor 250 is disposed on the opposite side of the roller restricting portion 241 a across the bearing 245, that is, in the vicinity of the end portion side peripheral surface of the pressure roller 231. In addition, as shown in FIG. 17, the thermistor 250 is disposed between the peripheral surface of the pressure roller 231 with a gap F in a state where the bearing 245 is not damaged. The gap F is smaller than the gap E between the pressure roller 231 and the roller restricting portion 241a. Further, in the illustrated example, the thermistor 250 is supported by a part of the roller pressing arm 242 via a spring 251 as a detection unit urging means. As shown in FIG. 18, when the pressure roller 231 is dropped due to the breakage of the bearing 245, the peripheral surface of the pressure roller 231 comes into contact with the thermistor 250, and the thermistor 250 is dropped along with the pressure roller 231. Can be displaced.

  The thermistor 250 outputs a voltage value corresponding to the detected temperature. Therefore, in this embodiment, when the temperature detected by the thermistor 250 exceeds a predetermined temperature, that is, when the voltage value of the thermistor 250 exceeds a predetermined voltage value, the CPU 400 stops driving the fixing motor 240. . A determination flow for such contact detection will be described with reference to FIG. First, the CPU 400 confirms the voltage value of the thermistor 250 as needed (S21), and determines whether or not the voltage value exceeds a predetermined voltage value (S22). When the voltage value exceeds a predetermined voltage value, the driving of the fixing motor 240 is stopped as an error. In the present embodiment, the operation of the image forming apparatus 100 is stopped. At this time, the user may be notified by an operation screen or an alarm.

  This will be specifically described. When the pressure roller 231 falls off (moves toward the roller restricting portion 241a) due to breakage of the bearing 245, the pressure roller 231 comes into contact with the thermistor 250 facing with a gap smaller than the gap E with the roller restricting portion 241a. At this time, the thermistor 250 is biased toward the pressure roller 231 by the spring 251, and the thermistor 250 moves in the same direction while being in contact with the pressure roller 231, so that the pressure roller 231 is in contact with the roller restricting portion 241 a. Abut. Thus, when the thermistor 250 contacts the pressure roller 231 heated by the heater 234, the temperature detected by the thermistor 250 rises and the voltage value of the thermistor 250 also rises. When the voltage value exceeds a predetermined voltage value, the CPU 400 determines that the bearing 245 is damaged, and stops the operation of the image forming apparatus. The predetermined current value is a value that is increased with some margin from the normal voltage value of the thermistor 250 facing the pressure roller 231 through the gap F when the bearing 245 is not damaged. . For example, although it depends on the size of the gap F, it is preferable to set it to 1.2 times, 1.5 times, etc. with respect to a value set as a normal voltage value so that erroneous detection is less likely to occur.

  In the case of this embodiment, since the detection temperature of the thermistor 250 detects that the pressure roller 231 is in contact with the roller restricting portion 241a, it can be seen that the bearing 245 is damaged. In this case, since the CPU 240 stops driving the fixing motor 240, it is possible to prevent parts such as gears from being damaged due to the damage of the bearing 245.

  In the above description, the thermistor is used as the temperature detection unit, but the same effect can be expected even when a detection element having a current interruption function such as a thermoswitch is used. That is, the temperature detection unit is cut off when the detected temperature exceeds a predetermined temperature, and the CPU 400 stops driving the fixing motor 240 when the temperature detection unit is cut off.

<Third Embodiment>
A third embodiment of the present invention will be described with reference to FIGS. In the second embodiment described above, the thermistor 250 as a temperature detection unit is arranged separately from the roller restricting unit. However, in this embodiment, the thermistor 250 also serves as the roller restricting unit. Since other configurations and operations are the same as those of the second embodiment described above, overlapping illustrations and descriptions are omitted or simplified, the same reference numerals are given to equivalent configurations, and the second embodiment is hereinafter described. It demonstrates centering on a different part.

  In the present embodiment, the thermistor 250 is fixed to a part of the pad pressure arm 241. And the part which opposes the surrounding surface of the pressure roller 231 of the thermistor 250 is made into the roller control part 250a. The gap E between the roller restricting portion 250a and the arm contact portion 231a of the pressure roller 231 is smaller than the gap C where the pressure roller 231 and the heater 234 are closest to each other (C> E).

  This will be specifically described. When the pressure roller 231 falls off due to breakage of the bearing 245, the pressure roller 231 contacts the roller restricting portion 250a of the thermistor 250 as shown in FIG. As a result, similarly to the second embodiment, the detection temperature of the thermistor 250 rises, and the CPU 400 can detect the breakage of the bearing 245. In the case of this embodiment as well, as in the second embodiment, a detection element having a current interruption function such as a thermo switch may be used as the temperature detection unit.

  In this embodiment, the thermistor 250 receives the weight and pressure of the pressure roller 231. Therefore, the pad pressure arm is more effective than the configuration in which the thermistor is biased by a spring as in the second embodiment. The structure fixed to the support part such as is desirable.

<Other embodiments>
In each of the above-described embodiments, the case where the present invention is applied to the pressure belt unit side has been described. However, the present invention can be applied to the fixing belt unit side as long as it has a heating source such as a halogen heater in a roller that stretches the belt for heating the fixing belt. In addition to the ball bearing using a steel ball as the rolling element as described above, the bearing supporting the roller may be a roller bearing using a roller as the rolling element, a needle bearing using a needle, or the like.

  In each of the above-described embodiments, the case where the present invention is applied to a belt-type fixing device has been described. However, the present invention can also be applied to other configurations. For example, the present invention can be applied to a configuration in which a roller is used instead of at least one of the fixing belt and the pressure belt. In other words, the present invention can be applied to both a configuration in which the fixing nip portion is formed by a pair of rollers and a configuration in which the fixing nip portion is formed by a roller and a belt. Even in such a configuration, if a heater is disposed in the roller, the roller and the heater may come into contact with each other due to damage to the bearing that supports the roller, and the heater may be damaged. Furthermore, the present invention is not limited to the fixing device, and can be applied to any configuration in which a heater such as a halogen heater is held in the roller separately from the roller.

  27 ... fixing device (heating device) / 230 ... pressure belt / 231 ... pressure roller (roller) / 231a ... arm contact portion / 232 ... pressure tension roller / 233 .... Pressure pad / 234 ... Heater (heating source) / 241 ... Pad pressure arm / 241a, 241b, 241c, 250a ... Roller regulating part / 241d ... Base / 241e ... Friction Material / 242 ... Roller pressure arm / 243 ... Pad pressure spring / 244 ... Roller pressure spring (first biasing means) / 245 ... Bearing / 245a ... Inner ring / 245b ..Outer ring / 245c: Steel ball (rolling element) / 250 ... Thermistor (temperature detection unit) / 251 ... Spring (detection unit biasing means) / 300b ... Tension spring (second biasing) Means) / 400 ... CPU ( Control means) / 401 ... current detection unit (contact sensing unit, a torque detection unit) /

Claims (14)

Laura,
A heating source disposed within the roller;
A bearing that rotatably supports the roller with respect to a support portion;
A holding part for holding the heating source separately from the roller with respect to the support part;
A roller restricting portion that is disposed in a direction in which the roller can move when the bearing is damaged at a position off the bearing of the roller, and restricts the movement of the roller;
In the state where the bearing is not damaged, when the gap between the position where the roller and the heating source are closest is C, and the gap between the roller and the roller restricting portion is E,
C> E
Meet,
A heating device characterized by that. Laura,
A heating source disposed within the roller;
A bearing that rotatably supports the roller with respect to a support portion;
A holding part for holding the heating source separately from the roller with respect to the support part;
A roller restricting portion that is disposed to face the peripheral surface of the roller removed from the bearing and restricts movement of the roller;
The bearing has an inner ring, an outer ring, and a plurality of rolling elements provided between the inner ring and the outer ring so as to be freely rollable.
In the state where the bearing has the plurality of rolling elements, D is a gap at a position where the inner ring and the outer ring are closest to each other, C is a gap at a position where the roller and the heating source are closest to each other, and When the clearance between the surface and the roller restricting portion is E,
D>C> E
Meet,
A heating device characterized by that. The bearing supports the axial end portion of the roller,
The roller restricting portion is disposed closer to the axial center of the roller than the bearing.
The heating apparatus according to claim 1, wherein the heating apparatus is characterized. A belt stretched by the roller;
A rotating body that rotates in contact with the outer peripheral surface of the belt;
First biasing means for applying a contact pressure between the belt and the rotating body;
Second urging means for applying tension to the belt,
The roller restricting portion is disposed in a resultant direction of a force acting on the roller by at least the urging force of the first urging means and a force acting on the roller by the urging force of the second urging means.
The heating apparatus according to any one of claims 1 to 3, wherein the heating apparatus is characterized in that The heating source is configured by providing a heating element that generates heat when energized in a glass tube.
The heating apparatus according to any one of claims 1 to 4, wherein the heating apparatus is characterized by the above. A drive source for driving the roller;
A contact detection unit for detecting that the roller and the roller regulating unit are in contact with each other;
Control means for stopping driving of the drive source when the contact detection unit detects that the roller and the roller restricting unit are in contact with each other;
The heating device according to any one of claims 1 to 5, wherein The contact detection unit is a torque detection unit that detects a value related to the drive torque of the drive source,
The control means stops driving of the drive source when a value detected by the torque detection unit exceeds a predetermined threshold.
The heating apparatus according to claim 6, wherein: The drive source is a motor;
The torque detector is a current detector that detects a current value applied to the motor,
The control means stops driving the drive source when the current value detected by the current detection unit exceeds a predetermined current value;
The heating device according to claim 7, wherein: The roller restricting portion has a concavo-convex shape on the surface facing the roller.
The heating device according to claim 7 or 8, characterized in that. The roller restricting portion includes a base and a friction material having a friction coefficient larger than that of the surface provided on the surface of the base facing the roller.
The heating device according to claim 7 or 8, characterized in that. The contact detection unit is a temperature detection unit that is disposed close to the surface of the roller and detects the surface temperature of the roller.
The control means stops driving of the drive source when the temperature detected by the temperature detection unit exceeds a predetermined temperature.
The heating apparatus according to claim 6, wherein: The temperature detector is turned off when the detected temperature exceeds a predetermined temperature,
The control means stops the driving of the driving source when energization of the temperature detection unit is interrupted,
The heating apparatus according to claim 11, wherein A detection unit urging means for urging the temperature detection unit toward the roller;
The temperature detection unit moves in contact with the surface when the roller moves toward the roller regulating unit by the urging force of the detection unit urging means.
The heating apparatus according to claim 11 or 12, characterized in that. The temperature detecting unit also serves as the roller regulating unit.
The heating apparatus according to claim 11 or 12, characterized in that.

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