JP2015166793A - Fixation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixation device which maintains excellent slidability between a fixation film and a nip forming member over a long period, and which hardly allows a slide torque to rise.SOLUTION: A fixation device includes: a fixation film which has flexibility and rotates; heating means for heating the fixation film; a nip forming member provided in contact with the inner surface of the fixation film; a lubricant present between the fixation film and a sliding part of the nip forming member; a pressure roller which pressure-contacts with the nip forming member with the fixation film interposed therebetween to form a nip part; and drive means for rotating the pressure roller. A heating device rotates the pressure roller to rotate the fixation film accordingly, sandwiches and conveys a recording material to the nip part, and applies pressure and heat to the recording material at the nip part. The heating device has a mode for reducing the gap between the fixation film and the nip forming member generated in the entrance or exit of a pressure contact nip.

Description

  The present invention relates to an electrophotographic fixing device capable of forming an image on a recording material such as a multifunction machine, a copying machine, a printer, and a fax machine.

  In an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, a toner image is formed on a sheet, and the image is formed by fixing the image by heating and pressing it. As such a fixing device, a roller fixing method in which a fixing nip is formed by pressing a pressure roller against a fixing roller having a heater therein to perform fixing is conventionally employed.

  By the way, in recent years, from the viewpoint of energy saving promotion, a film heating type fixing device that heats through a fixing film with a small heat capacity, that is, a film fixing device, has been proposed as an on-demand method with high heat transfer efficiency and quick start-up of the device. (See Patent Documents 1 to 4).

  The film fixing device includes, for example, a ceramic heater (hereinafter referred to as a heater) as a fixed and supported heating body, and a heat resistant resin film (hereinafter referred to as a fixing film) as a heat transfer member that slides with the heater. And an elastic pressure roller as a pressure member that forms a fixing nip portion as a toner image heating fixing region by pressing against the heater through the fixing film, and a fixing film and a pressure roller in the fixing nip portion, A recording material carrying an unfixed toner image is sandwiched and conveyed between them, and the unfixed toner image is heated and melt-fixed on the recording material by heat from a heater via a fixing film.

  The ceramic heater is held by a resin having high heat resistance (hereinafter referred to as a nip forming member), and the fixing film and the ceramic heater and the fixing film and the heater holder slide when the fixing film rotates.

  Since the fixing film of the film fixing apparatus as described above is thin, has a small heat capacity, and has a good thermal response, the thermal response of the heater can be reflected almost directly in the fixing nip portion. Therefore, the fixing temperature can be reached in a shorter time than when the heater is turned on (on-demand system), and power saving associated therewith is realized.

  In these fixing devices, it is necessary to better maintain the slidability of the fixing film and the ceramic heater, and the fixing film and the nip holder. Therefore, a lubricant such as silicon oil or grease is applied to the inner surface of the fixing film (see Patent Document 5).

JP-A-63-313182 Japanese Patent Laid-Open No. 2-157878 JP-A-4-44075 JP-A-4-204980 JP 2008-139775 A

  However, in the above fixing device, lubricant such as grease is accumulated in the nip forming members on the upstream side and the downstream side in the fixing belt rotation direction, and the grease on the inner surface of the belt is reduced. As a result, there is a problem that the sliding torque between the fixing film and the heater holder increases.

  When the increase in torque exceeds the allowable range, the recording material slips without being conveyed at the nip portion.

  Therefore, the present invention has been made in view of the above circumstances, and an object of the present invention is to improve the fixing film and the nip forming member in a fixing device including the fixing film and the nip forming member provided on the inner surface thereof. It is to provide a fixing device that maintains a good slidability for a long period of time and hardly increases the sliding torque.

  The above problems are solved by a fixing device and an image forming apparatus described below.

  According to a first aspect of the present invention, there is provided a rotating fixing film having flexibility, a heating means for heating the fixing film, a nip forming member provided in contact with the inner surface of the fixing film, and the fixing rotating body. A lubricant interposed between the nip forming member sliding portions, a pressure roller that presses against the nip forming member via the fixing film to form a nip portion, and a driving unit that rotates the pressure roller. A heating apparatus that rotates the pressure roller to rotate the fixing film and conveys the recording material in the nip portion, and heats and presses the recording material in the nip portion. A fixing device having a mode for narrowing a gap between the fixing film and the nip forming member.

  2. The fixing device according to claim 1, further comprising a vibration unit configured to vibrate the guide member in a moving direction of the transfer material, and having a mode of vibrating the guide member at a predetermined timing. .

  The fixing device according to claim 2, wherein the predetermined timing is when the pressure is released.

  According to a fourth aspect of the present invention, there is provided a moving unit that moves the separation guide member arranged in a non-contact manner with the fixing rotating body and on the downstream side of the nip, and the separation guide member moves at a predetermined timing. The fixing device according to claim 1, further comprising a mode in which a fixing film is pressed against the guide member.

  5. The fixing device according to claim 4, wherein the predetermined timing is after the transfer material passes through the fixing device and after the rotation of the fixing rotating body is stopped.

  A sixth aspect of the present invention is characterized in that the driving means is a motor and includes means for detecting a current of the motor, and the predetermined timing is when the current exceeds a predetermined value. The fixing device according to any one of claims 2 to 5.

  The fixing device according to any one of claims 2 to 5, wherein the predetermined timing is every predetermined number of sheets to be passed.

  According to the first invention, the gap between the fixing rotator and the guide member generated at the entrance or exit of the pressure nip is reduced, so that the lubricant swept out from the fixing nip adheres to the inner surface of the belt and is fixed. Can be returned to the nip.

  According to the second invention, the gap generated between the belt and the belt can be reduced by vibrating the guide member, and the lubricant swept from the fixing nip can be attached to the inner surface of the belt and returned to the fixing nip.

  According to the third invention, the guide member is vibrated when the pressure is released, so that the lubricant swept out of the fixing nip can be more effectively adhered to the inner surface of the belt and returned to the fixing nip.

  According to a fourth aspect of the present invention, the separation guide member is pressed against the fixing rotator to narrow the gap between the guide members, and the lubricant swept from the fixing nip is adhered to the inner surface of the belt, thereby fixing the fixing nip. It can be returned to.

  According to the fifth invention, after the transfer material passes through the fixing device and the rotation of the fixing rotator stops, the separation guide member is pressed against the fixing rotator to be more effectively swept out of the fixing nip. The lubricant can be adhered to the inner surface of the belt and returned to the fixing nip.

  According to the sixth aspect of the invention, the gap between the fixing rotating body and the guide member generated at the entrance or exit of the pressure nip is reduced only when the torque is increased, so that the downtime can be shortened.

  According to the seventh invention, the gap between the fixing rotator and the guide member generated at the entrance or exit of the press nip for each predetermined number of sheets is reduced, so that the downtime can be shortened without an extra cost increase. .

  According to the present invention, a flexible rotating fixing film, a heating means for heating the fixing film, a nip forming member provided in contact with the inner surface of the fixing film, the fixing rotating body, and the And a lubricant interposed between the sliding portions of the nip forming member, a pressure roller that presses the nip forming member through the fixing film to form the nip portion, and a driving unit that rotates the pressure roller. In the heating apparatus in which the fixing film is driven to rotate by rotating the pressure roller and the recording material is nipped and conveyed in the nip portion, and the recording material is heated and pressurized in the nip portion, at the entrance or exit of the pressure nip. By having a mode in which the gap between the generated fixing film and the nip forming member is reduced, the lubricant swept from the fixing nip adheres to the inner surface of the belt. It can be returned to the nip. As a result, it is possible to provide a fixing device that maintains good slidability between the fixing film and the nip-forming member over a long period of time and does not easily increase the sliding torque.

Sectional drawing explaining schematic structure of the image forming apparatus of this invention Sectional drawing explaining schematic structure of the fixing apparatus of this invention Sectional drawing explaining the positional relationship between the fixing film and the support member Sectional drawing explaining the positional relationship between the fixing film and the support member The figure explaining the schematic structure which vibrates the support member of this invention Sectional drawing explaining the positional relationship between the fixing film and the support member Sectional drawing explaining the positional relationship between the fixing film and the support member Sectional drawing explaining the positional relationship between the fixing film and the support member Flowchart for vibrating the support member of the present invention Graph explaining the effect of the present invention The figure explaining the schematic structure which moves the separation guide member of this invention Sectional drawing explaining the positional relationship between the fixing film and the support member Flowchart for moving the separation guide member of the present invention Graph explaining the effect of the present invention

  Next, specific examples (examples) of the embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following examples.

  FIG. 1 is a cross-sectional view of a color electrophotographic printer that is an example of an image forming apparatus according to the present embodiment, and is a cross-sectional view along the sheet conveyance direction. In this embodiment, the color electrophotographic printer is simply referred to as “printer”.

  The sheet is a sheet on which a toner image is formed. Specific examples of the sheet include plain paper, a resin sheet that is a substitute for plain paper, cardboard, and overhead projector.

  The printer shown in FIG. 1 includes an image forming unit 10 for each color of Y (yellow), M (magenta), C (cyan), and Bk (black). The photosensitive drum 11 is charged in advance by a charger 12. Thereafter, a latent image is formed on the photosensitive drum 11 by the laser scanner 13. The latent image becomes a toner image by the developing device 14. The toner image on the photosensitive drum 11 is sequentially transferred by the primary transfer blade 17 to, for example, an intermediate transfer belt 31 that is an image carrier. After the transfer, the toner remaining on the photosensitive drum 11 is removed by the cleaner 15. As a result, the surface of the photosensitive drum 11 becomes clean and prepares for the next image formation.

  On the other hand, the sheets P are sent one by one from the paper feed cassette 20 or the multi paper feed tray 25 and sent to the registration roller pair 23. The registration roller pair 23 receives the sheet P once, and straightens it when the sheet is skewed. The registration roller pair 23 feeds the sheet between the intermediate transfer belt 31 and the secondary transfer roller 35 in synchronization with the toner image on the intermediate transfer belt 31. The color toner image on the intermediate transfer belt is transferred onto the sheet P by, for example, a secondary transfer roller 35 which is a transfer body. Thereafter, the toner image on the sheet is fixed to the sheet by the sheet being heated and pressed by the fixing device 40.

  When a toner image is formed only on one side of the sheet, the sheet is discharged to the discharge tray 64 disposed on the side surface of the image forming apparatus 1 by switching the switching flapper 61 or the sheet is discharged from the image forming apparatus 1 side by side. The paper is discharged to a paper discharge tray 65 disposed on the upper surface of the forming apparatus 1. When the switching flapper 61 is at the broken line position, the sheet P is discharged face up (the toner image is on the upper side) onto the paper discharge tray 64, and when the switching flapper 61 is at the solid line position, the sheet P is Then, the sheet is discharged to the sheet discharge tray 65 face down (the toner image is on the lower side).

  When forming a toner image on both sides of the sheet, the sheet P on which the toner image is fixed by the fixing device 40 is guided upward by the flapper 61 located at the solid line, and when the trailing edge reaches the reversal point R, It is switched back by the conveyance path 73 and turned upside down. Thereafter, the sheet P is conveyed through the double-sided conveyance path 70, and a toner image is formed on the other side through the same process as the single-sided image formation, and is discharged onto the paper discharge tray 64 or the paper discharge tray 65. . The portion constituted by the flapper 61, the switchback conveyance path 73, and the like is an example of a reversing unit.

  Next, the fixing device 40 will be described in detail.

  FIG. 2 is a schematic configuration diagram of the fixing device 40, which is a heating device of a film heating method of a pressure rotating body driving method (tensionless type).

  Reference numeral 100 denotes a ceramic heater (hereinafter referred to as a heater) as a heating body. This heater 100 is basically composed of a thin and thin plate-like ceramic substrate whose longitudinal direction is perpendicular to the drawing, and an energization heating resistor layer provided on the surface of the substrate. It is a low heat capacity heater that raises the temperature with a good rise characteristic. In the present embodiment, a heating resistor layer is formed on a ceramic substrate having a thickness of 600 μm.

  Reference numeral 17 denotes a nip forming member that fixes and supports the heater 100. The nip forming member 17 is a heat insulating member such as a heat resistant resin having a substantially semicircular arc shape in cross section and having a longitudinal direction in the drawing as a longitudinal direction. The heater 100 is disposed in a groove formed along the length of the lower surface of the nip forming member 17 so that the heater surface is exposed downward and fixed with a heat resistant adhesive or the like.

  Reference numeral 20 denotes a cylindrical (endless) heat-resistant fixing film as a heating member that transfers heat, and is loosely fitted to the nip forming member 17 including the heater 100 described above. In order to reduce the heat capacity and improve the quick start property, the fixing film 20 has a film thickness of 100 μm or less, preferably 50 μm or less and 20 μm or more of heat-resistant PTFE, PFA, FEP monolayer, Alternatively, a composite layer film in which PTFE, PFA, FEP or the like is coated on the outer peripheral surface of polyimide, polyamideimide, PEEK, PES, PPS or the like can be used. It can also be made of metal. Moreover, you may provide a silicon rubber layer and a fluororubber layer as an elastic layer on the said base material as needed. Further, a fluororesin layer as a toner release layer, specifically, a PFA tube layer, a PTFE coating layer, or the like may be provided. In this embodiment, a fixing film having an inner diameter of 30 mm in which a silicon rubber layer of 300 μm is provided on a polyimide of 60 μm and a PFA tube layer of 30 μm is provided on the outermost layer is used.

  A stay 18 is disposed inside the nip forming member 17 and supports the nip forming member 17.

  As the material of the stay, SUS or iron that can give strength can be used. In this embodiment, SUS having a thickness of 3.0 mm is used.

  Reference numeral 22 denotes a heat-resistant elastic pressure roller as a pressure member, which includes a cored bar 22a and an elastic layer 22b made of a heat-resistant rubber such as silicon rubber or fluorine rubber, or a foam of silicon rubber, and both ends of the cored bar 22a. The part is disposed so as to be rotatably supported by a bearing. In this embodiment, a silicon rubber layer having a thickness of 3.5 mm is provided on an iron core metal having a diameter of 11.5 mm, and a PFA tube layer 50 μm as a toner release layer is provided on the outermost layer.

  The assembly of the heater 100, the nip forming member 17, the fixing film 20, and the stay 18 is arranged above the pressure roller 22 in parallel with the pressure roller 22 with the heater 100 facing downward, and the stay 18 is not shown. The lower surface of the heater 100 is pressed against the upper surface of the pressure roller 22 through the fixing film 20 against the elasticity of the roller elastic layer by fixing the biasing member with a biasing member, and fixing with a predetermined width as a heating unit. A nip portion N is formed.

  The pressure roller 22 is rotated in the counterclockwise direction indicated by an arrow by a driving unit 24 controlled by the DC controller 45 through a gear (not shown) attached to an end portion in the longitudinal direction (direction perpendicular to the paper surface). It is rotationally driven at the peripheral speed. A rotational force acts on the cylindrical fixing film 20 by the pressure frictional force at the fixing nip N between the pressure roller 22 and the fixing film 20 by the rotational driving of the pressure roller 22, and the fixing film 20 is attached to the heater 100. The support member 17 is rotated in the clockwise direction indicated by the arrow Y while sliding in close contact with the downward surface. The support member 17 is also a rotation guide member for the cylindrical fixing film 20.

  The pressure roller 22 is driven to rotate, and the cylindrical fixing film 20 is driven and rotated. The heater 100 is energized, and the heater quickly rises to a predetermined temperature and is adjusted in temperature. In this state, the recording material P carrying the unfixed toner image t is introduced between the fixing film 20 and the pressure roller 22 in the fixing nip N, and the toner image carrying side surface of the recording material P is fixed in the fixing nip N. The fixing nip N is held and conveyed together with the fixing film 20 in close contact with the outer surface of the film 20. In this nipping and conveying process, the recording material P is heated by the heat of the fixing film 20 heated by the heater 100, and the unfixed toner image t on the recording material P is heated and pressurized on the recording material P to be melt-fixed. . The recording material P that has passed through the fixing nip N is separated from the surface of the fixing film 20 and is discharged and conveyed.

  Here, heat-resistant grease is applied to the inner surface of the fixing film 20 in order to ensure good slidability with the heater 100 and the nip forming member 17. In this embodiment, heat resistant grease HP-830 manufactured by Toray Dow Corning Co., Ltd. is used. Here, FIG. 3 is an enlarged view of a region A surrounded by a dotted circle in FIG. As the fixing film rotates, heat-resistant grease is accumulated on the surface B of FIG. This is because the heat-resistant grease on the inner surface of the fixing film is scraped by the nip forming member 17 and accumulates on the surface B. As a result, there is a problem that the grease applied to the inner surface of the belt is reduced and the sliding torque is increased. It is also conceivable that the distance C is set to zero as shown in FIG. 4 in order not to accumulate grease on the surface B in FIG. However, as shown in FIG. 4, when the distance C is set to zero, the fixing film and the supporting member suddenly come into contact with each other at point E, and a large force is applied to the fixing film to scrape the inner surface of the fixing film, so that the sliding torque is more likely to increase. The problem of becoming. Therefore, in the fixing device having the configuration of the present embodiment, as shown in FIG. 4, the distance C is kept to some extent so that the fixing film and the support member can be gradually brought into contact with each other. The same applies to the region D surrounded by the dotted circle in FIG. Whether the heat-resistant grease is accumulated in the region A or the region D depends on the shape of the nip forming member 17.

  Furthermore, considering that heat-resistant grease accumulates on the surface B in advance, it may be possible to increase the grease on the inner surface of the fixing film. However, even if there is too much heat-resistant grease, the grease becomes a lump at the nip portion N, hindering the heat conduction from the heater to the film, or the pressure applied to the transfer material at the nip portion becomes uneven. Problems arise.

  Therefore, in this embodiment, when the pressure is released, the nip forming member 17 is vibrated in the moving direction of the transfer material to reduce the distance C, and the heat-resistant grease accumulated on the surface B is adhered to the inner surface of the fixing film to be swept away. Return to the nip. FIG. 5A is a schematic configuration diagram for vibrating the nip forming member 17. The nip forming member 17 is vibrated in a direction parallel to the transfer material traveling direction at a predetermined timing by the vibrating means 55 controlled by the DC controller 45. At the time of pressurization, there is a certain distance between the fixing film and the nip forming member in the areas A and D as shown in FIG. 5B. As shown in c) and (d), the distance between the fixing film and the nip forming member can be reduced in the area A and the area D, respectively. Further, a fixing motor torque detection device is attached to the fixing device 40 and is vibrated only when the value of the motor torque exceeds 7.2 kgf · cm. Thereby, since the nip forming member 17 is vibrated only when the torque is increased, the downtime can be shortened. FIG. 6 shows a flowchart for vibrating the nip forming member 17.

  Step 1: The torque during paper passing is measured by a torque detector attached to the fixing motor. When the motor torque value does not exceed 7.2 kgf · cm, the driving is stopped and the process is terminated after the paper is passed.

  Step 2: Stop driving after the end of paper feeding.

  Step 3: Pressure release.

  Step 4: The nip forming member is vibrated for a predetermined time.

  Step 5: Stops the vibration of the nip forming member and ends.

  Using the fixing device of the present embodiment, a paper passing durability test was repeated for passing three sheets of paper. Since another study determined that the paper could not be conveyed when the torque value exceeded 7.5 kgf · cm, the test was terminated when the torque exceeded 7.5 kgf · cm. “Paper cannot be transported” means that even if the pressure roller is rotated by the fixing motor, the fixing film does not rotate, and as a result, the paper slips and is not transported in the fixing device. Accordingly, the number of sheets that can be passed until the torque reaches 7.5 kgf · cm is referred to as the durable number. FIG. 7 shows the transition of the endurance torque of the fixing device and the fixing device which does not vibrate the nip forming member of this embodiment. It can be seen that in the fixing device that does not vibrate the nip forming member, the durable sheet number is 330 k, whereas in the present embodiment, the durable sheet number is 450 k, and the durable sheet number increases. This is because “heat-resistant grease is accumulated on the B surface in FIG. 3 when the paper is passed” → “When the pressure is released, the nip forming member is vibrated, so that the distance C is reduced and the B surface is The accumulated grease is returned to the inner surface of the fixing belt "→" Slidability between the fixing belt and the nip forming member is improved ", so that durability can be achieved if the nip forming member is vibrated when pressure is released. The number is considered to have increased. In fact, the torque increases little by little because of scraping from the inner surface of the fixing film and the nip forming member, but the grease accumulated on the B surface is returned to the inner surface of the fixing film. Thus, this increase in torque is suppressed.

  The image forming apparatus in the present embodiment is the same as the image forming apparatus in the first embodiment, but the fixing device 40 is different.

  In the present embodiment, after the transfer material passes through the fixing device and the rotation of the fixing rotator stops, the separation guide member 28 disposed in the non-contact and downstream of the nip is fixed to the fixing rotator. Is pressed against the guide member so that the heat resistant grease adheres to the inner surface of the fixing film and the swept away grease is returned to the nip. The separation guide member 28 is moved in a direction parallel to the transfer material advancing direction at a predetermined timing by the driving means 27 controlled by the DC controller 45 and contacts the fixing film. At the time of driving, there is a certain distance between the fixing film and the nip forming member in the region D as shown in FIG. 8A, but when the driving is stopped, the separation guide member 28 is moved and brought into contact with the fixing film. As shown in (b), the distance between the fixing film and the nip forming member can be reduced in the region D. Since the separation guide member 28 is brought into contact with the fixing film, a Teflon (registered trademark) tape is stuck on the surface of the separation guide member 28 so that the surface of the fixing film is not damaged at the time of contact.

  Further, every time the number of sheets passed exceeds a predetermined number, after completion of the sheet passing, the separation guide member 28 is pressed against the fixing film after the rotation of the fixing film is stopped. Thereby, downtime can be shortened without an extra cost increase. FIG. 9 shows a flowchart for pressing the separation guide member against the fixing film.

  Step 1: Count the total number of sheets that are being fed. If the number of sheets passed does not exceed an integral multiple of 50,000 sheets, the driving is stopped and the process is terminated after the sheet passing.

  Step 2: Stop driving after the end of paper feeding.

  Step 3: Move the separation guide member by a predetermined distance.

  Step 4: End the separation guide member by returning it to a predetermined position.

  FIG. 10 shows changes in the durability torque of the fixing device and the fixing device in which the separation guide member is not moved. In the fixing device in which the separation guide member is not moved, the durable sheet number is 350k, whereas in the present embodiment, the durable sheet number is 450k, and the durable sheet number is increased.

11. Photosensitive drum 12. Drum charger 13. Laser scanner 14. Developer 15. Cleaner 23. Registration roller pair 25. Multi-feed tray 31. Intermediate transfer belt 35. Secondary transfer roller 40. Fixing device 61. Switching flapper 63. Paper discharge roller 64. Paper discharge tray 65. Discharge tray 100. Ceramic heater

Claims (7)

A rotating fixing film having flexibility, a heating means for heating the fixing film, a nip forming member provided in contact with the inner surface of the fixing film, and a sliding portion of the fixing film and the nip forming member sliding portion. A lubricant interposed therebetween, a pressure roller that press-contacts with the nip forming member via the fixing film to form a nip portion, and a driving unit that rotates the pressure roller, and the pressure roller In the heating device that rotates the fixing film by rotating and conveys the recording material in the nip portion, and heats and presses the recording material in the nip portion,
A fixing device having a mode in which a gap between the fixing film and the nip forming member generated at the entrance or exit of the press nip is reduced.   The fixing device according to claim 1, further comprising a vibration unit configured to vibrate the nip forming member in a moving direction of the transfer material, and having a mode for vibrating the nip forming member at a predetermined timing.   The fixing device according to claim 2, wherein the predetermined timing is when pressure is released.   There is provided a moving means for moving a separation guide member arranged on the downstream side of the nip in a non-contact manner with the fixing rotating body, the separation guide member moves at a predetermined timing, and the fixing film is used as the guide member. The fixing device according to claim 1, further comprising a pressing mode.   The fixing device according to claim 4, wherein the predetermined timing is after the transfer material passes through the fixing device and after the rotation of the fixing rotating body is stopped.   6. The driving device according to claim 2, wherein the driving means is a motor and includes means for detecting a current of the motor, and the predetermined timing is when the current exceeds a predetermined value. The fixing device according to claim 1.   The fixing device according to claim 2, wherein the predetermined timing is every predetermined number of sheets to be passed.