JP2014170180A - Fixing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of preventing toner powder or paper powder from accumulating on a contact-type temperature detection unit with a low contact pressure to make the temperature detection unit dirty.SOLUTION: A fixing device comprises: an endless fixing belt 32; a pressure roller 33 that applies pressure to the fixing belt 32; a heat transfer member 31 that has a heater 36 inside and transfers heat from the heater 36 to the fixing belt 32; and a stationary member 35 that is provided inside the fixing belt 32 to bring the fixing belt 32 into pressure contact with the pressure roller 33. The fixing device passes a recording medium through a press-contact part between the pressure roller 33 and the fixing belt 32. The fixing device further includes a thermistor 42 that is brought into contact with an outer peripheral surface of the pressure roller 33 to detect a temperature of the outer peripheral surface, a pressing mechanism 50 that presses the thermistor 42 against the outer surface of the pressure roller 33, and a sweeping member 56 that can be in contact or separated with/from the outer peripheral surface of the pressure roller 33. The sweeping member 56 is arranged on the downstream side of the thermistor 42 along a direction of rotation of the pressure roller 33.

Description

  The present invention relates to a fixing device and an image forming apparatus equipped with the fixing device.

  Conventionally, a heat roller fixing device is known as a fixing device used in an image forming apparatus such as a printer or a copying machine. This heat roller fixing device has a heat source such as a halogen lamp inside, and is provided with two rotating bodies (fixing roller and pressure roller) that are pressed against each other and rotated while being heated. Then, by passing the recording medium through a nip portion (pressure contact portion) where the outer peripheral surfaces of the two rotating bodies are in contact with each other, the unfixed toner image on the recording medium is melted and fixed.

  In addition, a heating roller having a heat source is generally used for the fixing device. However, in recent years, an endless belt member such as a belt or a thin film is used instead of the heating roller due to an increasing demand for energy saving and waiting time reduction. It has been adopted. By adopting an endless belt member, the heat capacity of the fixing device can be reduced, and the efficiency of heat transfer to the recording medium can be improved. As a result, it is possible to realize a so-called on-demand type fixing device in which the waiting time required for heating (warm-up time and first print time) is significantly shortened.

  In this type of fixing device, a fixing member that contacts the belt member is provided, and the fixing member is slid while contacting the fixing member on the inner peripheral surface of the belt member, and the fixing member is pressed against the rotating body via the belt member. As a result, a nip portion is formed between the belt member and the rotating body. As in the case of the fixing device having the heating roller, the toner image can be fixed on the recording medium by passing the recording medium through the nip portion.

  Further, this type of fixing device is provided with a temperature detecting means for detecting the temperature of the pressure roller and the belt member. As such a temperature detection means, a contact-type temperature detection unit (thermistor) that contacts an outer surface of a pressure roller or a belt member is known.

  By the way, if the contact-type temperature detection unit is kept in contact with the outer surface of the pressure roller or belt member, a small amount of toner powder or paper powder accumulates on the contact-type temperature detection unit over a long period of use. It becomes difficult to accurately detect the temperature of the belt member.

  Therefore, in the conventional image forming apparatus, for the purpose of removing dirt from the contact-type temperature detection unit, a cleaning paper is wound around the fixing member in contact with the contact-type temperature detection unit, and this cleaning paper is used as the contact-type temperature detection unit. It has been proposed to clean the contact-type temperature detecting unit by passing between the fixing member and the fixing member (see, for example, Patent Document 1).

  However, in recent years, a low contact pressure type is used for the contact type temperature detection unit in order to reduce a load caused by contact with a detection target. For this reason, in the conventional cleaning method depending on the contact pressure of the contact-type temperature detection unit, there is a problem in that the contamination of the temperature detection unit cannot be efficiently removed.

  Although there is a non-contact type temperature detection unit, this non-contact type temperature detection unit has a time lag until temperature detection, and cannot be used for a fixing device of a type that raises temperature in a short time in recent years.

  SUMMARY OF THE INVENTION An object of the present invention is to mount a fixing device capable of preventing toner powder and paper powder from accumulating on a contact-type temperature detection unit having a low contact pressure and causing contamination on the temperature detection unit, and the fixing device. An object is to provide an image forming apparatus.

  In order to solve the above-described problems, the present invention provides an endless belt member, a pressure rotating body that pressurizes the belt member while rotating in contact with the belt member, and supports the belt member, And a heat transfer member that transmits heat from the heat source to the belt member, and a fixing member that is provided inside the belt member and supports the belt member from the inside and press-contacts the pressurizing rotating body. A fixing device that fixes an unfixed toner image on the recording medium by passing the recording medium through a pressure contact portion between the pressure rotator and the belt member, on the outer peripheral surface of the pressure rotator. A contact-type temperature detection unit that detects the temperature of the pressurizing rotating body by contact, a pressing mechanism that presses the contact-type temperature detecting unit against the outer surface of the pressurizing rotating body, A wiping member capable of contacting and separating, Member may be arranged on the downstream side of the contact-type temperature detecting unit along the rotational direction of the pressure rotating body.

  According to the present invention, the contact-type temperature detection unit is pressed against the outer surface of the pressure rotator by the pressing mechanism, the dirt adhering to the contact-type temperature detection unit is transferred to the pressure rotator, and then the pressurization is performed. The dirt transferred to the rotating body can be wiped off with the wiping member. As a result, it is possible to prevent toner powder and paper powder from accumulating on the contact-type temperature detection unit with a low contact pressure and causing contamination on the temperature detection unit.

1 is a diagram schematically illustrating an internal configuration of a color electrophotographic apparatus that is an image forming apparatus. FIG. FIG. 2 is a diagram illustrating in detail an internal configuration of a fixing device. 2 is a diagram illustrating in detail an internal configuration of a fixing device according to Embodiment 1. FIG. It is a flowchart explaining a series of operation | movement of a press mechanism and a wiping member contact / separation mechanism. It is a flowchart which shows the cleaning sequence when the usage-amount of a recording medium etc. are considered. FIG. 5 is a diagram illustrating in detail an internal configuration of a fixing device according to a second embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

Example 1
FIG. 1 schematically shows an internal configuration of a color electrophotographic apparatus 10 which is an image forming apparatus. As shown in FIG. 1, the color electrophotographic apparatus 10 includes four process cartridges 11 (11C, 11M, 11Y, and 11K), a transfer belt 12, an exposure device 13, and a fixing device 14. The process cartridge 11 is disposed almost at the center in the machine frame of the image forming apparatus.

  The transfer belt 12 is installed below the process cartridge 11 and is wound around rollers 16 and 17 to move in the direction of arrow A. The transfer belt 12 moves while being sandwiched between an image carrier 18 in the process cartridge 11 and a first transfer roller 19 disposed to face the image carrier 18.

  The exposure device 13 is disposed above the process cartridge 11. The exposure device 13 is for forming a latent image on the image carrier 18 in the process cartridge 11, and has a polygon mirror 20, a reflection mirror 21, and a lens (not shown) as an optical system. ing.

  Below the transfer belt 12, a paper feed cassette 23 in which recording media 22 are loaded and stored is disposed. A paper feeding device 24 is provided on the upper side of the paper feeding cassette 23, and the paper feeding device 24 feeds the recording medium 22 in the paper feeding cassette 23 one by one. The fed recording medium 22 passes between the transfer belt 12 near the roller 17 and the second transfer roller 26 via the conveying roller pair 25 and is guided to the fixing device 14 disposed on the side of the process cartridge 11. It is burned. Examples of the recording medium 22 include paper and an OHP sheet.

  Then, by applying a high potential to the first transfer roller 19, a potential difference is generated between the image carrier 18 and the transfer belt 12, and the toner image formed on the outer peripheral surface of the image carrier 18 is transferred to the transfer belt. 12 is transferred.

  The process cartridge 11 includes a cyan process cartridge 11C, a magenta process cartridge 11M, a yellow process cartridge 11Y, and a black process cartridge 11K. As the transfer belt 12 moves in the direction of arrow A, the toner images for each color are sequentially transferred to the transfer belt 12 by the process cartridges 11K, 11Y, 11M, and 11C, and a single color toner image is transferred onto the transfer belt 12. A plurality of color toner images are formed by superimposing the images.

  The recording medium 22 is supplied from the conveying roller pair 25 to the second transfer roller 26 by the paper feeding device 24 in synchronization with the movement of the transfer belt 12. Then, by applying a high potential to the second transfer roller 26, a potential difference is generated between the transfer belt 12 and the second transfer roller 26. As a result, the single color or color toner image formed on the surface of the transfer belt 12 is transferred onto the recording medium 22.

  The recording medium 22 onto which the toner image (unfixed toner image) has been transferred is peeled off from the transfer belt 12 and sent to the fixing device 14 where the toner image is melted and fixed on the recording medium 22. Thereafter, the recording medium 22 is discharged from a paper discharge device 27 provided above the fixing device 14 to a paper discharge tray 28 on the upper surface of the color electrophotographic apparatus 10.

  After the toner image is transferred to the recording medium 22, excess toner remaining on the surface of the transfer belt 12 is cleaned by the transfer belt cleaning device 29 and collected by the toner collecting device 30 below the transfer belt 12. The cleaned transfer belt 12 is sent to the process cartridge 11 to prepare for the transfer of the next toner image.

  FIG. 2 is a diagram showing the internal configuration of the fixing device 14 in detail. As shown in FIG. 2, the fixing device 14 includes a heat transfer member 31, a fixing belt 32 provided around the heat transfer member 31, and a pressure roller 33 disposed to face the heat transfer member 31 and the fixing belt 32. I have. Here, the fixing belt 32 constitutes a belt member, and the pressure roller 33 constitutes a pressure rotator.

  The heat transfer member 31 has a cylindrical shape, and a plate-like reinforcing member (support member) 34 is provided therein. Further, an opening 31A is formed in a part of the cylindrical surface of the heat transfer member 31 along the axial direction of the heat transfer member 31 (perpendicular to the paper surface in FIG. 2). In addition, attachment portions 31B and 31C bent in an L-shaped cross section are provided.

  A reinforcement member (support member) 34 is provided inside the heat transfer member 31. The reinforcing member 34 has a plate shape, and a fixing member 35 is provided on one side (right side in FIG. 2). The fixing member 35 is disposed in the opening 31A of the heat transfer member 31, is in contact with the back surface of the fixing belt 32, and is entirely housed in the concave space S in the mounting portions 31B and 31C. Yes. Further, a plurality of heaters 36 as heat sources are provided inside the heat transfer member 31, and the heat transfer member 31 is heated by these heaters 36.

  The pressure roller 33 has a cored bar 37 at the center thereof. A contact / separation mechanism 38 that moves the pressure roller 33 in the directions of arrows B1 and B2 is provided at one end (or both ends) of the pressure roller 33. That is, the contact / separation mechanism 38 moves the pressure roller 33 closer to the heat transfer member 31 and the fixing belt 32, and separates the pressure roller 33 from the heat transfer member 31 and the fixing belt 32.

  The contact / separation mechanism 38 includes a pressure lever 39 whose intermediate portion contacts the outer peripheral surface of the cored bar 37 of the pressure roller 33, a pressure spring 40 connected to the upper portion of the pressure lever 39, and the pressure spring 40. An eccentric cam 41 that contacts the holding plate 40A and rotates about a shaft 41A is provided. The pressure lever 39 has a lower end supported by a support shaft 39A and is rotatable in the directions of arrows C1 and C2 around the support shaft 39A.

  Further, a thermistor 42 as a contact type temperature detector is provided outside the pressure roller 33, and the thermistor 42 contacts the outer peripheral surface of the pressure roller 33 to measure the temperature of the pressure roller 33. To do.

  The thermistor 42 includes a temperature detection unit 42A that performs temperature measurement, and a support unit 42B that supports the temperature detection unit 42A. The temperature detection unit 42A has a spring property (elasticity), and measures the temperature of the pressure roller 33 by lightly contacting the outer surface of the pressure roller 33 by the spring property.

  The fixing belt 32 is a thin and flexible endless belt, and rotates (runs) in the direction of arrow D (counterclockwise) in FIG. In the fixing belt 32, a base material layer, an elastic layer, and a release layer are sequentially laminated from the inner peripheral surface side, and the total thickness thereof is set to 1 mm or less.

  Said base material layer is 30-100 micrometers in thickness, and is formed with resin materials, such as metal materials, such as nickel and stainless steel, and a polyimide. The elastic layer has a layer thickness of 100 to 300 μm and is made of a rubber material such as silicone rubber, foamable silicone rubber, or fluororubber. By providing this elastic layer, minute irregularities on the surface of the fixing belt 32 at the nip portion (pressure contact portion) are not formed, and heat is uniformly transmitted to the toner image T on the recording medium 22 to suppress the occurrence of a cocoon skin image. The Further, the release layer has a layer thickness of 10 to 50 μm, and includes PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, PES (polyether). (Sulfide) and other materials. By providing this release layer, releasability (peelability) for the toner T (toner image) is ensured.

  The diameter of the fixing belt 32 (the outer diameter of the fixing belt 32 when the fixing belt 32 is cut along a plane perpendicular to its axis) is set to 15 to 120 mm. In this embodiment, the diameter of the fixing belt 32 is set to about 30 mm.

  The pressure roller 33 that contacts the outer peripheral surface of the fixing belt 32 at the nip portion has a diameter of about 30 to 40 mm, and an elastic layer 43 is formed on a hollow core metal 37. The elastic layer 43 is formed of a material such as foamable silicone rubber, silicone rubber, or fluororubber. A thin release layer made of PFA, PTFE or the like can be provided on the surface layer of the elastic layer 43. The pressure roller 33 has a drum shape, and the difference in diameter between the center and the end is 0.05 to 0.25 mm. The pressure roller 33 is in pressure contact with the fixing belt 32, and a desired nip portion is formed on both the pressure roller 33 and the fixing belt 32.

  The fixing member 35 is made of a heat resistant resin material such as a liquid crystal polymer. By providing an elastic member such as silicone rubber or fluororubber between the fixing member 35 and the fixing belt 32, the belt surface follows the minute irregularities on the surface of the recording medium 22 at the nip portion, so that the recording medium 22 The heat is uniformly transmitted to the toner image T. Thereby, the effect of prevention of the cocoon skin image generation can be expected.

  The fixing member 35 has a concave cross-sectional shape so that the surface on the side in contact with the pressure roller 33 follows the curvature of the pressure roller 33. Thereby, since the recording medium 22 is sent out from the nip portion so as to follow the curvature of the pressure roller 33, it is possible to suppress a problem that the recording medium 22 after the fixing process is not attracted to the fixing belt 32 and separated. it can.

  In FIG. 2, the cross section of the fixing member 35 on the side where the nip portion is formed is formed in a concave shape, but the cross section is formed in a flat shape or formed so as to continuously change from a flat shape to a concave shape. You can also. By making the nip portion an arbitrary shape, when the shape of the nip portion is substantially parallel to the image surface of the recording medium 22, there is an effect of preventing the recording medium 22 from being wrinkled. Further, by bringing the concave cross section closer, the adhesion between the fixing belt 32 and the recording medium 22 is increased, and the fixing property is improved. Further, since the curvature of the fixing belt 32 on the exit side of the nip portion is increased, the recording medium 22 fed from the nip portion can be easily separated from the fixing belt 32.

  The cylindrical heat transfer member 31 has a thickness of 0.2 mm or less. As a material of the heat transfer member 31, a metal heat conductor (a metal having heat conductivity) such as aluminum, iron, and stainless steel can be used. By setting the thickness of the heat transfer member 31 to 0.2 mm or less, the heating efficiency of the fixing belt 32 (heat transfer member 31) can be improved. The heat transfer member 31 is formed so as to be close to or in contact with the inner peripheral surface of the fixing belt 32 at a position excluding the nip portion. In addition, the heat transfer member 31 is formed in a concave shape in the opening 31A (that is, the portion where the nip portion is formed) by mounting portions 31B and 31C having an L-shaped cross section.

  Here, the gap between the fixing belt 32 and the heat transfer member 31 at normal temperature (gap at a position excluding the nip portion) is preferably greater than 0 mm and 1 mm or less (0 mm <A ≦ 1 mm). As a result, the area where the heat transfer member 31 and the fixing belt 32 are in contact with each other is increased, and a problem that wear of the fixing belt 32 is accelerated can be suppressed. Further, it is possible to suppress the problem that the heat transfer member 31 and the fixing belt 32 are too far apart to reduce the heating efficiency of the fixing belt 32.

  Furthermore, since the heat transfer member 31 is arranged close to the fixing belt 32, the circular posture of the flexible fixing belt 32 is maintained to some extent, so that deterioration and breakage due to deformation of the fixing belt 32 are reduced. be able to.

  Further, in order to reduce the frictional resistance between the heat transfer member 31 and the fixing belt 32, the contact surface of the heat transfer member 31 is formed of a material having a low friction coefficient, or the inner peripheral surface 32A of the fixing belt 32 contains fluorine. It is also possible to form a surface layer made of a material. In FIG. 2, the heat transfer member 31 is formed to have a substantially circular cross-sectional shape, but the heat transfer member 31 may be formed to have a polygonal cross-sectional shape.

  Further, when a means for uniformly transferring the heat from the heat transfer source to the fixing belt 32 and ensuring the running stability of the fixing belt 32 during driving is prepared separately, the heat transfer member 31 is not provided. It is also possible to configure a fixing device that directly transfers heat to the fixing belt 32. In that case, since the heat capacity of the heat transfer member 31 is excluded from the heat capacity of the entire fixing device, there is an advantage that a fixing device that is more excellent in temperature rise performance and energy saving performance can be configured.

  The reinforcing member (support member) 34 is for reinforcing and supporting the fixing member 35 forming the nip portion, and is fixed to the inner peripheral surface side of the fixing belt 32.

  Both ends of the heat transfer member 31 in the width direction are fixed and supported on a side plate (not shown) of the fixing device 14. The heat transfer member 31 is heated by the radiant heat (radiant light) of the heater 36 to heat the fixing belt 32. That is, the heat transfer member 31 is directly heated by the heater (heating means) 36, and the fixing belt 32 is indirectly heated by the heater 36 through the heat transfer member 31. The output control of the heater 36 is performed based on the detection result of the belt surface temperature by the temperature sensor 44 such as a thermistor facing the surface of the fixing belt 32. Further, the temperature of the fixing belt 32 (fixing temperature) can be set to a desired temperature by such output control of the heater 36.

  As described above, in the fixing device 14, not only a part of the fixing belt 32 is locally heated, but the fixing belt 32 is substantially entirely heated in the circumferential direction by the heat transfer member 31. Become. For this reason, even when the speed of the apparatus is increased, the fixing belt 32 is sufficiently heated, and the occurrence of fixing failure can be suppressed. In FIG. 2, a halogen heater is used as an example of the heater 36, but the type of the heat source is not limited to the halogen heater, and for example, a fixing device having an induction heating type heat source may be used.

  The reinforcing member 34 is formed so that the length in the width direction (perpendicular to the paper surface in FIG. 2) is equal to that of the fixing member 35, and both end portions in the width direction are formed on side plates (not shown) of the fixing device 14. Fixed and supported. The reinforcing member 34 contacts the pressure roller 33 via the fixing member 35 and the fixing belt 32, so that the fixing member 35 is greatly deformed by the pressure applied by the pressure roller 33 in the nip portion. Suppressed. The reinforcing member 34 is preferably formed of a metal material having high mechanical strength such as stainless steel or iron in order to satisfy the above-described function.

  Further, when the heater 36 is a heat source that uses radiant heat, such as a halogen heater, a heat insulating member is provided on a part or all of the surface of the reinforcing member 34 facing the heater 36, or BA treatment, A mirror polishing process can also be performed. Since radiant heat from the heater 36 toward the reinforcing member 34 (heat for heating the reinforcing member 34) is used for heating the heat transfer member 31, the heating efficiency of the fixing belt 32 (heat transfer member 31) is further improved. It will be.

  The pressure roller 33 is provided with a gear that meshes with a drive gear of a drive mechanism (not shown), and the pressure roller 33 is rotationally driven in the direction of arrow E (clockwise) in FIG. Further, both ends of the pressure roller 33 in the width direction are rotatably supported by side plates (not shown) of the fixing device 14 via bearings. A heat source such as a halogen heater can be provided inside the pressure roller 33. Further, when the elastic layer 43 of the pressure roller 33 is formed of a sponge-like material such as foamable silicone rubber, the applied pressure acting on the nip portion can be reduced, so that the bending generated in the fixing member 35 is reduced. can do.

  Further, since the heat insulation of the pressure roller 33 is enhanced and the heat of the fixing belt 32 is less likely to move to the pressure roller 33 side, the heating efficiency of the fixing belt 32 is improved. In FIG. 2, the diameter of the fixing belt 32 is formed to be equal to the diameter of the pressure roller 33, but the diameter of the fixing belt 32 may be formed to be smaller than the diameter of the pressure roller 33. In that case, since the curvature of the fixing belt 32 at the nip portion is smaller than the curvature of the pressure roller 33, the recording medium 22 delivered from the nip portion is easily separated from the fixing belt 32. In addition, the diameter of the fixing belt 32 can be formed to be larger than the diameter of the pressure roller 33, but the pressure roller 33 is independent of the relationship between the diameter of the fixing belt 32 and the diameter of the pressure roller 33. It is preferable to configure so that the applied pressure does not act on the heat transfer member 31.

  Furthermore, as described above, the fixing device 14 is provided with the contact / separation mechanism 38 that contacts and separates the pressure roller 33 from the fixing belt 32. The contact / separation mechanism 38 includes a pressure lever 39, a pressure spring, and the like. 40, an eccentric cam 41, and the like. Among these, the support shaft 39A of the pressure lever 39 is rotatably supported by a side plate (not shown) of the fixing device 14. When the pressure lever 39 rotates about the support shaft 39 </ b> A in the direction of the arrow C <b> 1, the central portion of the pressure lever 39 comes into contact with the bearing of the pressure roller 33. Note that. The bearing of the pressure roller 33 is movably held in a long hole formed in a side plate (not shown) of the fixing device 14.

  The pressure lever 39 is provided with an eccentric cam 41 via a pressure spring 40. When the eccentric cam 41 is rotated by a drive motor (not shown), the pressure lever 39 rotates in the direction of arrow C. As a result, the pressure roller 33 moves in the direction of the arrow B1. That is, during the normal fixing process, the eccentric cam 41 is rotated in the rotational direction as shown in FIG. 2, and the pressure roller 33 presses the fixing belt 32 to form a desired nip portion.

  On the other hand, when it is not during the normal fixing process (during jamming or standby), the eccentric cam 41 rotates 180 degrees from the state shown in FIG. The roller 33 separates from the fixing belt 32 (or depressurizes the fixing belt 32).

  The normal operation of the fixing device 14 configured as described above will be briefly described below. When the power switch of the color electrophotographic apparatus 10 is turned on, electric power is supplied to the heater 36 and the pressure roller 33 is rotated in the direction of arrow E. As a result, the fixing belt 32 is also driven (rotated) in the direction of arrow D by the frictional force with the pressure roller 33. Thereafter, the recording medium 22 is fed from the paper feeding device 24 (see FIG. 1), and an unfixed color image is carried (transferred) on the recording medium 22 at the position of the second transfer roller 26. The recording medium 22 carrying the unfixed image T (toner image) is conveyed in the direction of the arrow F1 while being guided by a guide plate (not shown), and a nip portion between the fixing belt 32 and the pressure roller 33 in a pressure contact state. To be sent to. The toner on the surface of the recording medium 22 is heated by the fixing belt 32 heated by the heat transfer member 31 (heater 36) and the pressing force of the fixing member 35 reinforced by the reinforcing member 34 and the pressure roller 33. The image T is fixed. Thereafter, the recording medium 22 sent out from the nip portion is conveyed in the direction of arrow F2.

  Next, the characteristic part of a present Example is demonstrated using FIG.

  In this embodiment, a pressing mechanism 50 that presses the thermistor 42 is provided on the outer peripheral surface of the pressure roller 33. The pressing mechanism 50 includes an L-shaped pressing member 51 for pressing the temperature detection unit 42A of the thermistor 42, a solenoid 52 that operates when the pressing member 51 presses the temperature detection unit 42A, and a pressing member 51. And a tension spring 53 for returning to a non-operating state. The pressing member 51 is connected to the solenoid 52. The pressing member 51 has an L-shaped bent portion supported by a support shaft 54, and the pressing member 51 is rotatable about the support shaft 54. Further, the tension spring 53 is attached to the end portion of the pressing member 51 on one side and to the fulcrum 55 on the other side.

  A wiping member 56 for wiping the outer peripheral surface of the pressure roller 33 is provided on the downstream side of the thermistor 42 along the rotation direction of the pressure roller 33. The wiping member 56 is supported by a wiping member contact / separation mechanism 57, and is brought into contact with and separated from the pressure roller 33 by the operation of the wiping member contact / separation mechanism 57. That is, the wiping member 56 is pressed against the outer surface of the pressure roller 33 or separated from the outer surface of the pressure roller 33 by the operation of the wiping member contact / separation mechanism 57.

  Note that the pressing mechanism 50 including the pressing member 51, the wiping member 56, and the wiping member contact / separation mechanism 57 are similarly moved along the arrows B1 and B2 when the pressure roller 33 moves in the directions of the arrows B1 and B2. Move in the direction.

  When the temperature detection part 42 </ b> A of the thermistor 42 becomes dirty and cleans, the solenoid 52 is driven to pull the pressing member 51 against the tensile force of the tension spring 53. Then, the pressing member 51 rotates about the support shaft 54 counterclockwise in the drawing, and the upper portion of the pressing member 51 comes into contact with the temperature detection unit 42A. The pressing member 51 strongly presses the temperature detection unit 42 </ b> A against the outer peripheral surface of the pressure roller 33. Thereby, the dirt adhering to the temperature detection part 42A of the thermistor 42 is transferred (rubbed) to the outer peripheral surface of the pressure roller 33.

  The transferred dirt moves in the direction of the wiping member 56 provided downstream as the pressure roller 33 rotates. At this time, the wiping member contacting / separating mechanism 57 is driven to bring the wiping member 56 into contact with the outer peripheral surface of the pressure roller 33. Thereby, the dirt transferred to the outer peripheral surface of the pressure roller 33 can be wiped off by the wiping member.

  FIG. 4 is a flowchart for explaining a series of operations of the pressing mechanism 50 and the wiping member contact / separation mechanism 57.

  When cleaning the temperature detection unit 42A of the thermistor 42, first, the pressing member 51 is driven, the temperature detection unit 42A is pressed by the tip of the pressing member 51, and the temperature detection unit 42A of the thermistor 42 is pressurized. Press strongly against the outer peripheral surface of the roller 33 (step S11). At the same time, the wiping member 56 is brought into contact with the outer peripheral surface of the pressure roller 33 (step S12).

  When the pressure roller 33 is rotated a predetermined number of times in the above state (step S13), the surface (pressure roller) of the temperature detection unit 42A is generated by the frictional force acting between the pressure roller 33 and the temperature detection unit 42A of the thermistor 42. Dirt adheres to the surface 33 on the side in contact with the outer peripheral surface of 33. However, since the temperature detection unit 42A is strongly pressed against the outer peripheral surface of the pressure roller 33 by the pressing member 51, the dirt adhering to the surface of the temperature detection unit 42A is transferred to the outer peripheral surface of the pressure roller 33. The dirt transferred to the outer peripheral surface of the pressure roller 33 is wiped off by the wiping member 56 on the downstream side of the thermistor 42.

  When the series of operations is completed, the pressing member 51 is separated from the outer peripheral surface of the pressure roller 33 (step S14), and the wiping member 56 is also separated from the outer peripheral surface of the pressure roller 33 (step S15).

  The dirt adhering to the temperature detector 42A of the thermistor 42 has a correlation with the amount of the recording medium 22 that passes through the fixing device 14. FIG. 5 is a flowchart showing a cleaning sequence considering this point.

  First, it is determined whether or not the number of recording media 22 (sheet passing count) passing through the fixing device 14 exceeds a threshold value (step S21). If exceeded, a cleaning sequence is executed (step S22). If not exceeded, the cleaning sequence is not executed and the process is terminated as it is.

  The activation of the cleaning sequence is determined as shown in FIG. 5 with the number or distance of the recording media 22 passing through the fixing device 14 as a threshold value. Accordingly, it is possible to prevent temperature detection abnormalities caused by dirt adhering to the temperature detection unit 42A while avoiding wear of the temperature detection unit 42A of the thermistor 42 and the outer surface of the pressure roller 33 due to unnecessary cleaning.

  Further, at this time, it is considered that when the temperature around the fixing device 14 is high, the toner melts and easily adheres to the temperature detection unit 42A of the thermistor 42. For this reason, the threshold value may be a value that is corrected according to the use environment, such as using a value calculated by multiplying the actual number of sheets to be passed by a factor of 1.5. As such an environmental condition, the coefficient may be changed depending on conditions such as a humidity state related to paper dust and the like, whether the paper is recycled paper, etc. in addition to the temperature.

  According to the present embodiment, the dirt adhering to the temperature detection unit 42A of the thermistor 42 is scraped off by rubbing against the outer peripheral surface of the pressure roller 33, and the temperature detection unit 42A can be maintained in a clean state at all times. As a result, the temperature of the pressure roller 33 can be accurately detected by the temperature detector 42A.

  In addition, since the cleaning sequence is executed in consideration of the amount of the recording medium 22 that passes through the fixing device 14, the cleaning is surely started when the stain progresses, and the possibility of erroneous temperature detection is reduced. Can do.

  In this embodiment, the threshold value for determining whether or not to execute the cleaning sequence is calculated by using a correction coefficient based on the use environment such as the temperature, humidity, or continuous paper passing state in the apparatus. Since the toner adhesion state changes depending on environmental factors such as temperature, the possibility of erroneous detection of temperature can be reduced by reflecting these environmental factors on the cleaning interval.

  Further, in the present embodiment, since the temperature detecting portion 42A of the thermistor 42 is pressed by the pressing member 51, the dirt on the temperature detecting portion 42A is applied more than when relying solely on the spring property of the temperature detecting portion 42A. It is possible to efficiently transfer to the outer surface of the pressure roller 33.

Example 2
FIG. 6 shows a second embodiment. In the present embodiment, the elastic member 60 is attached to the distal end portion of the pressing member 51 (the portion that contacts the temperature detection portion 42A of the thermistor 42). When dirt adheres to the temperature detection unit 42A, the surface of the temperature detection unit 42A becomes uneven, making it difficult to press the pressing member 51 against the temperature detection unit 42A with a constant force.

  If configured as in the present embodiment, even if the surface of the temperature detection unit 42A is dirty and uneven, the pressing member 51 can be reliably pressed against the temperature detection unit 42A with a certain force. Therefore, it is possible to easily transfer (rub against) the dirt adhering to the temperature detection unit 42 </ b> A to the outer peripheral surface of the pressure roller 33.

  In this embodiment, the width of the wiping member 56 (width in the direction perpendicular to the paper surface in FIG. 6) is wider than the width of the temperature detection unit 42A of the thermistor 42 (width in the direction perpendicular to the paper surface in FIG. 6). Yes. With this configuration, even if the dirt rubbed from the temperature detection unit 42A to the outer peripheral surface of the pressure roller 33 spreads beyond the width of the temperature detection unit 42A, the dirt can be surely wiped off by the wiping member 56. Can do. Such a configuration can also be applied to the case of the first embodiment.

  Although the embodiments of the present invention have been described in detail with reference to the drawings, each of the above embodiments is only an example of the present invention, and the present invention is not limited only to the configuration of each of the above embodiments. . Needless to say, changes in design and the like within the scope of the present invention are included in the present invention.

  For example, although the L-shaped pressing member 51 is used in each of the above embodiments, the temperature detection unit 42A of the thermistor 42 is pressed against the outer peripheral surface of the pressure roller 33 using an eccentric cam or the like. May be.

10 Color electrophotographic device (image forming device)
11 Process cartridge 12 Transfer belt (belt member)
13 Exposure Device 14 Fixing Device 22 Recording Medium 31 Heat Transfer Member 32 Fixing Belt 33 Pressure Roller (Pressure Rotating Body)
35 Fixing member 36 Heater (heat source)
42 Thermistor (Contact temperature detector)
42A Temperature Detection Unit 50 Pressing Mechanism 51 Pressing Member 52 Solenoid 56 Wiping Member 57 Wiping Member Contacting / Separating Mechanism 60 Elastic Member

JP 2008-304514 A

Claims (7)

An endless belt member, a pressurizing rotating body that pressurizes the belt member while rotating in contact with the belt member, and supports the belt member, and has a heat source inside, and heat from the heat source is A heat transfer member that transmits to the belt member; and a fixing member that is provided inside the belt member and supports the belt member from the inside and press-contacts with the pressure rotator, the pressure rotator and the belt member A fixing device for fixing an unfixed toner image on the recording medium by passing the recording medium through the press contact portion of
A contact-type temperature detection unit that detects the temperature of the pressurizing rotator in contact with the outer peripheral surface of the pressurizing rotator;
A pressing mechanism that presses the contact-type temperature detection unit against an outer surface of the pressurizing rotating body;
A wiping member that can be contacted and separated from the outer peripheral surface of the pressure rotating body,
The fixing device, wherein the wiping member is disposed downstream of the contact-type temperature detecting unit along a rotation direction of the pressure rotating body.   The fixing device according to claim 1, wherein the pressure rotator rotates in a state where the pressing mechanism presses the contact-type temperature detection unit.   The pressing operation by the pressing mechanism is performed when the number of sheets of the recording medium or the sheet passing distance that has passed through the pressure contact portion between the pressing rotator and the belt member exceeds a threshold value. The fixing device according to 1 or 2.   The fixing device according to claim 1, wherein the threshold value is calculated using a correction coefficient based on a use environment such as temperature, humidity, or continuous paper passing state in the device. .   The fixing device according to claim 1, wherein the pressing mechanism is provided with an elastic member at a contact portion with the contact-type temperature detection unit.   The width along the axial direction of the pressurizing rotating body is such that the width of the wiping member is wider than the width of the contact-type temperature detection unit. Fixing device. An image forming apparatus equipped with the fixing device according to claim 1.