JP2007047674A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the durability of a film in a film type fixing device which adopts curvature separation as a system for separation by securing slidability between the film and a film support means and suppressing a bending load as much as possible. <P>SOLUTION: A heating means which has a cylindrical film member, the film support means of supporting the film member, a pressure member forming a nip by pressing the film member, and a slide member which slides the film member at the nip part and clamps a recording material at the nip part by the film member and pressure member and and conveys the recording material to fix an image on the recording material is provided with a step member which projects the film member from the slide member toward the pressure member to bend it nearby the nip along the length of the film support member orthogonal to the recording material conveying direction, and the quantity of projection of the step member toward the film member is variable. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing device section in an image forming apparatus such as a copying machine, a printer, a facsimile, or the like that forms an image by electrophotography.

  For convenience, an image heating apparatus (fixing apparatus) that is provided in an image forming apparatus such as a copying machine or a printer and that heats and fixes a toner image onto a recording material will be described as an example.

  In an image forming apparatus, a recording material (transfer material sheet, electrofax sheet, electrostatic recording paper, OHP sheet, printing paper, printing paper, electrophotographic process, electrostatic recording process, magnetic recording process, etc. As a fixing device that heats and fixes an unfixed image (toner image) of target image information formed and supported on a recording sheet or the like by a transfer method or a direct method as a permanently fixed image on a recording material surface, a heat roller device In recent years, belt heating systems have been put into practical use from the viewpoint of quick start and energy saving.

a) Film heating type fixing device Examples of the film heating type fixing device include JP-A-63-313182, JP-A-2-157878, JP-A-4-44075 and JP-A-4-204980. Has been proposed.

  That is, a nip portion is formed by sandwiching a heat-resistant film (fixing film) between a ceramic heater as a heating element and a pressure roller as a pressure member, and the film in the nip portion and the pressure roller The recording material on which an unfixed toner image to be image-fixed is formed and supported is introduced and conveyed together with the film so that the heat of the ceramic heater is applied to the recording material through the film at the nip portion. Further, the unfixed toner image is fixed to the surface of the recording material by heat and pressure by the applied pressure of the nip portion.

  This film heating type fixing device can be configured as an on-demand type device using a ceramic heater and a film having a low heat capacity as a film, and energizes the ceramic heater as a heat source only when the image forming apparatus performs image formation. It is only necessary to generate heat at a predetermined fixing temperature, and the waiting time from the power-on of the image forming apparatus to the image forming executable state is short (quick start property), and the power consumption during standby is greatly reduced (saving) Power).

b) Electromagnetic induction heating type fixing device Japanese Utility Model Laid-Open No. 51-109739 discloses an induction heating fixing device that induces a current in a fixing roller by magnetic flux and generates heat by Joule heat. This makes it possible to directly heat the fixing roller by using the generation of induced current, and achieves a fixing process that is more efficient than a heat roller type fixing device using a halogen lamp as a heat source.

  However, since the energy of the alternating magnetic flux generated by the exciting coil as the magnetic field generating means is used for raising the temperature of the entire fixing roller, the heat dissipation loss is large, and the fixing energy density with respect to the input energy is low and the efficiency is low.

  Therefore, in recent years, in order to obtain energy that affects fixing at high density, the excitation coil is brought close to the fixing roller, which is a heating element, or the alternating magnetic flux distribution of the excitation coil is concentrated in the vicinity of the fixing nip portion to achieve high efficiency. A fixing device has been devised.

  FIG. 2 is a schematic enlarged view of the fixing nip portion in the electromagnetic induction heating type fixing device.

  The fixing film 8a-1 is frictionally driven while being in pressure contact with the pressure roller 8b and the film supporting means 8a-2, and a low friction sliding member 8a-5 is provided at the sliding portion of the film supporting means with the fixing film. Further, grease is applied to the sliding portion in order to improve the slidability. The grease is configured to circulate along with the inner surface of the fixing film rotated by idling or recording material passing.

Further, a step 8a-6 as proposed in JP-A-9-152804 may be provided downstream of the sliding portion in the sheet passing direction, and the fixing film that has passed through the fixing nip N bends at this step. As the curvature of the outer peripheral surface of the fixing film increases, the separation ability of the recording material from the fixing film can be improved. In such a configuration, there is no need to install contact-type separation claws that are often used in high-speed machines. Improvements can be made.
Japanese Unexamined Patent Publication No. 9-152804

  By the way, as a condition that makes it difficult to separate from the fixing film, there is a case where toner is placed on the entire surface of a thin paper having no rigidity. As a method for dealing with such a case, a step downstream of the fixing nip (hereinafter, downstream) It is known that increasing the level difference is effective. However, since the downstream step becomes a repeated bending load on the driving fixing film, it greatly affects the durability of the fixing film. This is particularly noticeable in a fixing film having a metal base layer, and there is a problem that irregularities caused by cracking of the metal base layer appear in an image formed on the recording material even if the surface layer is not destroyed.

  In addition, by increasing the downstream step, the fixing film position approaches the recording material immediately after the fixing nip, so that the state of the toner image on the fixing nip side changes and affects the glossiness of the recording material. is there.

  In addition, as can be seen from FIG. 2, the downstream step has an action of blocking the grease used for lubrication and adhering to the inner surface of the fixing film, so that the contact pressure with the fixing film increases when the downstream step is increased, There is a problem that the grease necessary for lubricating the inner surface of the fixing film cannot be sufficiently turned. As a result, wear on the sliding member or the inner surface of the fixing film starts on the sliding surface with insufficient grease, causing various problems such as influence on the life of the fixing film, increase in driving torque, and generation of abnormal noise at the sliding portion. It becomes.

In order to solve the above problems, the first invention of the present application is a cylindrical film member, a film support means for supporting the film member, a pressure member for pressurizing the film member to form a nip, A heating member that has a sliding member that slides on the film member at the nip portion, and holds and conveys the recording material between the film member and the pressure member at the nip portion, and fixes the image on the recording material.
In the vicinity of the nip, a step member that protrudes and bends the film member toward the pressure member from the sliding member is provided in the longitudinal direction of the film support member perpendicular to the recording material conveyance direction, and the step member protrudes to the film member. The quantity is variable.

In order to solve the above problems, the second invention according to the present application includes a cylindrical film member, a film support means for supporting the film member, a pressure member for pressurizing the film member to form a nip, A heating member that has a sliding member that slides on the film member at the nip portion, and holds and conveys the recording material between the film member and the pressure member at the nip portion, and fixes the image on the recording material.
The protruding amount of the step member is changed according to the temperature of the film support member or the pressure member.

In order to solve the above problems, the third invention of the present application is directed to a cylindrical film member, film support means for supporting the film member, a pressure member for pressurizing the film member to form a nip, A heating member that has a sliding member that slides on the film member at the nip portion, and holds and conveys the recording material between the film member and the pressure member at the nip portion, and fixes the image on the recording material.
The step member is supported by a bimetal or a shape memory alloy having a laminated structure of a plurality of metals having different coefficients of thermal expansion.

In order to solve the above problems, the present invention relates to a fourth aspect of the present invention, a cylindrical film member, a film support means for supporting the film member, a pressure member for pressurizing the film member to form a nip, A heating member that has a sliding member that slides on the film member at the nip portion, and holds and conveys the recording material between the film member and the pressure member at the nip portion, and fixes the image on the recording material.
The step member is composed of an elastic member that is deformed by the rigidity of the recording material to be nipped and conveyed.

In order to solve the above problems, the fifth invention of the present application is directed to a cylindrical film member, film support means for supporting the film member, a pressure member for pressurizing the film member to form a nip, A heating member that has a sliding member that slides on the film member at the nip portion, and holds and conveys the recording material between the film member and the pressure member at the nip portion, and fixes the image on the recording material.
The protruding amount of the step member is changed by driving means using a piezoelectric element.

In order to solve the above problems, the sixth invention according to the present application includes a cylindrical film member, a film support means for supporting the film member, a pressure member for pressurizing the film member to form a nip, A heating member that has a sliding member that slides on the film member at the nip portion, and holds and conveys the recording material between the film member and the pressure member at the nip portion, and fixes the image on the recording material.
The protruding amount of the step member is changed by a driving means using an eccentric cam.

In order to solve the above problems, the seventh invention according to the present application is a cylindrical film member, a film support means for supporting the film member, a pressure member for pressurizing the film member to form a nip, A heating member that has a sliding member that slides on the film member at the nip portion, and holds and conveys the recording material between the film member and the pressure member at the nip portion, and fixes the image on the recording material.
The protruding amount of the step member is changed by driving means using an electromagnet.

In order to solve the above problems, the eighth invention of the present application provides a cylindrical film member, a film support means for supporting the film member, a pressure member for pressurizing the film member to form a nip, A heating member that has a sliding member that slides on the film member at the nip portion, and holds and conveys the recording material between the film member and the pressure member at the nip portion, and fixes the image on the recording material.
The protruding amount of the step member is changed by a signal of a recording material detection sensor disposed in the recording material conveyance path.

In order to solve the above problems, the ninth invention of the present application is a cylindrical film member, a film support means for supporting the film member, a pressure member for pressurizing the film member to form a nip, A heating member that has a sliding member that slides on the film member at the nip portion, and holds and conveys the recording material between the film member and the pressure member at the nip portion, and fixes the image on the recording material.
The protruding amount of the step member is changed by a signal from any one of a paper thickness detection sensor, an OHT detection sensor, a gloss detection sensor, and a temperature / humidity sensor disposed in the recording material conveyance path.

In order to solve the above problems, the tenth invention according to the present application is an image forming means for forming a toner image on an image carrier, and a toner image formed on the image carrier is transferred to a recording material. A transfer means; a fixing device for fixing the toner image transferred onto the recording material;
In an image forming apparatus having
A cylindrical film member, film support means for supporting the film member, a pressure member that pressurizes the film member to form a nip, and a sliding member that slides on the film member in the nip portion, In the heating means for nipping and conveying the recording material between the film member and the pressure member in the nip portion and fixing the image on the recording material,
The protruding amount of the step member is changed within the recording material width detected by the width detection means of the recording material to be conveyed.

  As described above, according to the first to seventh aspects of the present invention, the load on the fixing film, the circulation amount of the sliding grease, the fixing film The posture can be changed, and high durability and high quality output of the fixing film can be obtained.

  According to the eighth and ninth inventions of the present application, the recording material characteristics can be automatically detected by the recording material detection sensor, so that the user does not need to manually switch the downstream step protrusion amount, and the user makes an incorrect setting. This can be prevented.

  Further, according to the tenth aspect of the present application, it is possible to set the protrusion amount change area of the downstream step according to the width of the recording material to be passed, and to minimize the load on the fixing film. As a result, the durability of the fixing film can be improved.

Example 1
Embodiments of the present invention will be described below with reference to the drawings.

{Overall configuration of color image forming apparatus}
First, the overall configuration of the color image forming apparatus will be outlined with reference to FIG. FIG. 1 is a cross-sectional view showing the overall configuration of a full-color laser beam printer 100 that is an embodiment of a color image forming apparatus.

  A color image forming apparatus 100 shown in the figure includes four photosensitive drums 1a, 1b, 1c, and 1d arranged in parallel in the horizontal direction. The photosensitive drum 1 is rotationally driven clockwise in the figure by a driving means (not shown). A charging device 2 (2a, 2b, 2c, 2d) for uniformly charging the surface of the photosensitive drum 1 in order according to the rotation direction, and a laser beam is irradiated around the photosensitive drum 1 based on image information. A scanner unit 3 (3a, 3b, 3c, 3d) for forming an electrostatic latent image on the drum 1, and a developing device 4 (4a, 4b, 4c, 4d) for developing the toner image by attaching toner to the electrostatic latent image ), An electrostatic transfer device 5 that transfers the toner image on the photosensitive drum 1 to the recording material S, and a cleaning device 6 (6a, 6b, 6c, which removes transfer residual toner remaining on the surface of the photosensitive drum 1 after transfer). 6d) and the like are provided.

  Here, the photosensitive drum 1, the charging device 2, the developing device 4, and the cleaning device 6 are integrated into a cartridge to form a process cartridge 7.

  Hereinafter, the photosensitive drum 1 will be described in detail.

  The photoconductor drum 1 is configured by applying an organic photoconductive layer (OPC photoconductor) to the outer peripheral surface of an aluminum cylinder having a diameter of 30 mm, for example. The photosensitive drum 1 is rotatably supported at both ends by a support member, and is driven to rotate clockwise by transmitting a driving force from a drive motor (not shown) to one end. .

  As the charging device 2, a contact charging type can be used. The charging member is a conductive roller formed in a roller shape. The roller is brought into contact with the surface of the photosensitive drum 1 and the surface of the photosensitive drum 1 is made uniform by applying a charging bias voltage to the roller. To be charged.

  The scanner unit 3 is arranged substantially above the photosensitive drum 1, and image light corresponding to an image signal is rotated at high speed by a scanner motor (not shown) by a laser diode (not shown). , 9c, 9d). The image light reflected by the polygon mirror 9 selectively exposes the surface of the charged photosensitive drum 1 through the imaging lens 10 (10a, 10b, 10c, 10d) to form an electrostatic latent image. It is composed.

  Each of the developing devices 4a, 4b, 4c, and 4d is composed of a developing device that stores toner of each color of yellow, magenta, cyan, and black.

An electrostatic transfer belt 11 that circulates and moves so as to face and contact all the photosensitive drums 1a, 1b, 1c, and 1d is disposed. The electrostatic transfer belt 11 is formed of a film-like member having a thickness of about 150 μm and having a volume resistivity of 10 ¹¹ to 10 ¹⁴ Ω · cm. This electrostatic transfer belt 11 is supported by rollers in four horizontal directions in a horizontal direction, and circulates and moves so that the recording material S is electrostatically adsorbed on the outer peripheral surface on the left side in the drawing to bring the recording material S into contact with the photosensitive drum 1. To do. As a result, the recording material S is conveyed to the transfer position by the electrostatic transfer belt 11 and the toner image on the photosensitive drum 1 is transferred.

  The transfer roller 12 (12a, 12b, 12c, 12d) is arranged in parallel at a position in contact with the inside of the electrostatic transfer belt 11 and facing the four photosensitive drums 1a, 1b, 1c, 1d. A positive charge is applied from the transfer roller 12 to the recording material S via the electrostatic transfer belt 11, and a negative polarity on the photosensitive drum 1 is applied to a sheet in contact with the photosensitive drum 1 by an electric field by the charge. The toner image is transferred.

  The electrostatic transfer belt 11 is a belt having a circumferential length of about 700 mm and a thickness of 150 μm. The belt is stretched by four rollers, that is, a driving roller 13, driven rollers 14 a and 14 b, and a tension roller 15, and rotates in the direction of the arrow in the figure. Thereby, the toner image is transferred while the above-described electrostatic transfer belt 11 circulates and the recording material S is conveyed from the driven roller 14a side to the driving roller 13 side.

  The paper feeding unit 16 feeds and conveys the recording material S to the image forming unit, and a plurality of recording materials S are stored in the paper feeding cassette 17. At the time of image formation, the paper feed roller 18 (half-moon roller) and the registration roller pair 19 are driven and rotated according to the image forming operation to separate and feed the recording material S in the paper feed cassette 17 one by one, and at the front end of the recording material S , Abuts against the registration roller pair 19 and temporarily stops. After forming a loop, the rotation of the electrostatic transfer belt 11 and the image writing position are synchronized, and the sheet is fed to the electrostatic transfer belt 11 by the registration roller pair 19. .

  The recording material S to which the respective color toner images are sequentially transferred while being conveyed by the electrostatic attraction belt 11 is then fixed by being heated and pressed by the fixing unit 8.

  As an image forming operation, the process cartridges 7a, 7b, 7c, and 7d are sequentially driven in accordance with the print timing, and the photosensitive drums 1a, 1b, 1c, and 1d are driven to rotate clockwise in accordance with the drive. Is done. Then, the scanner units 3 corresponding to the respective process cartridges 7 are sequentially driven. By this driving, the charging roller 2 imparts a uniform charge to the circumferential surface of the photosensitive drum 1, and the scanner unit 3 exposes the circumferential surface of the photosensitive drum 1 according to the image signal to perform photosensitive drum 1. An electrostatic latent image is formed on the peripheral surface. The developing roller in the developing device 4 transfers (transfers) the toner to the low potential portion of the electrostatic latent image to form (develop) the toner image on the circumferential surface of the photosensitive drum 1.

  At the timing when the leading edge of the toner image on the circumferential surface of the most upstream photosensitive drum is rotated and conveyed to a point facing the electrostatic transfer belt 11, the printing start position of the recording material S coincides with that point. Then, the registration roller pair 19 starts to rotate and feeds the recording material S to the electrostatic transfer belt 11.

  The recording material S is pressed against the outer periphery of the electrostatic transfer belt 11 so as to be sandwiched between the electrostatic adsorption roller 22 and the electrostatic transfer belt 11, and a voltage is applied between the electrostatic transfer belt 11 and the electrostatic adsorption roller 22. When applied, the recording material S that is a dielectric and the dielectric layer of the electrostatic transfer belt 11 are induced, and the recording material is electrostatically attracted to the outer periphery of the electrostatic transfer belt 11. Thereby, the recording material S is stably adsorbed to the electrostatic transfer belt 11 and conveyed to the most downstream transfer portion.

  While being conveyed in this manner, the toner image on each photosensitive drum 1 is sequentially transferred to the recording material S by an electric field formed between each photosensitive drum 1 and the transfer roller 12.

  The recording material S to which the four color toner images have been transferred is separated from the electrostatic transfer belt 11 by the curvature separation ability based on the curvature of the belt driving roller 13 and is carried into the fixing unit 8.

  After the toner image is thermally fixed by the fixing unit 8, the recording material S is discharged to the paper discharge unit 24 by the paper discharge roller pair 23.

  Here, an electromagnetic induction heating type fixing device will be described as an example of the fixing unit 8.

  FIG. 3 shows a schematic configuration of an example of an electromagnetic induction heating type fixing device that improves the efficiency by concentrating the alternating magnetic flux distribution of the exciting coil in the fixing nip.

  8a-1 is a cylindrical fixing film having an electromagnetic induction heat generating layer (conductor layer, magnetic layer, resistor layer) as an electromagnetic induction heat generating rotating body.

  8a-2 is a saddle-shaped film guide member having a substantially semicircular cross section, and the cylindrical fixing film 8a-1 is loosely fitted outside the film guide member 8a-2.

  A magnetic field generating means comprising an exciting coil 8a-3 and an E-type magnetic core (core material) 8a-4 is disposed inside the film guide member 8a-2.

  Reference numeral 8b denotes an elastic pressure roller. The fixing film 8a-1 is sandwiched between the lower surface of the film guide member 8a-2 and a fixing nip portion N having a predetermined width is formed with a predetermined pressing force so as to be pressed against each other. The magnetic core 8a-4 of the magnetic field generating means is disposed so as to correspond to the fixing nip N.

  The pressure roller 8b is rotationally driven in the counterclockwise direction indicated by the arrow by the driving means. A rotational force acts on the fixing film 8a-1 by a frictional force between the pressure roller 8b and the outer surface of the fixing film 8a-1 due to the rotational driving of the pressure roller 8b, and the inner surface of the fixing film 8a-1 is changed. At the fixing nip portion N, the outer periphery of the film guide member 8a-2 has a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 8b in the clockwise direction as indicated by an arrow while sliding in close contact with the lower surface of the film guide member 8a-2. In a rotating state (pressure roller drive system).

  The film guide member 8a-2 pressurizes the fixing nip, supports the exciting coil 8a-3 and magnetic core 8a-4 as magnetic field generating means, supports the fixing film 8a-1, and rotates the film 8a-1. It serves to improve the transport stability at the time. The film guide member 8a-2 is an insulating member that does not hinder the passage of magnetic flux, and a material that can withstand a high load is used.

  The exciting coil 8a-3 generates an alternating magnetic flux by an alternating current supplied from an unillustrated exciting circuit. The alternating magnetic flux is intensively distributed in the fixing nip portion N by the E-type magnetic core 8a-4 corresponding to the position of the fixing nip portion N, and the alternating magnetic flux is electromagnetic in the fixing film 8a-1 in the fixing nip portion N. An eddy current is generated in the induction heating layer. This eddy current generates Joule heat in the electromagnetic induction heating layer by the specific resistance of the electromagnetic induction heating layer.

  The electromagnetic induction heat generation of the fixing film 8a-1 occurs intensively in the fixing nip N where the alternating magnetic flux is intensively distributed, and the fixing nip N is heated with high efficiency.

  The temperature of the fixing nip portion N is controlled so that a predetermined temperature is maintained by controlling the current supply to the exciting coil 8a-3 by a temperature control system including a temperature detection unit (not shown).

  Thus, the pressure roller 8b is driven to rotate, and the cylindrical fixing film 8a-1 rotates around the outer periphery of the film guide member 8a-2, and the above-mentioned power is supplied from the excitation circuit to the excitation coil 8a-3. As described above, in the state where the electromagnetic induction heat generation of the fixing film 8a-1 is performed and the fixing nip portion N rises to a predetermined temperature and is temperature-controlled, the unfixed toner image t conveyed from the image forming unit (not shown) is The formed recording material S is introduced between the fixing film 8a-1 and the pressure roller 8b in the fixing nip N so that the image surface faces upward, that is, opposite to the fixing film surface. Is in close contact with the outer surface of the fixing film 8a-1, and is conveyed through the fixing nip N together with the fixing film 8a-1. In the process in which the recording material S is nipped and conveyed together with the fixing film 8a-1 through the fixing nip N, the fixing film 8a-1 is heated by electromagnetic induction heat generation, and the unfixed toner image t on the recording material S is obtained. Is fixed by heating.

  When the recording material S passes through the fixing nip N, the recording material S is separated by the curvature of the pressure roller 8b, the film guide member 8a-2, and the fixing film 8a-1.

  The feature of this embodiment is that the amount of protrusion of the downstream step to the fixing film can be made variable to ensure the circulation of sliding grease and the durability of the fixing film.

  In this embodiment, the downstream step member 8a-6 is held by the shape memory alloy biasing means 8a-8 and the bias biasing means 8a-7. Here, the state where the temperature of the fixing unit can be raised and output can be seen in the state of FIG. 3, and FIG. 4 shows the state where the temperature has not risen sufficiently.

  For example, in the state of FIG. 4 such as immediately after the image forming apparatus is turned on, the temperature around the downstream step member 8a-6 is low, and the bias urging means 8a-7 has a lower urging force than the urging force of the shape memory alloy urging means 8a-8. The urging force is superior, and the projecting amount of the downstream step member 8a-6 to the fixing film 8a-1 is suppressed.

  When an output signal is input from the outside to the main body of the image forming apparatus, the heating unit rotates the fixing film by the pressure roller 8b until the fixing temperature rises to a predetermined fixing temperature. 4 until the urging force of the shape memory alloy urging means 8a-8 overcomes the urging force of the bias urging means 8a-7 to reach the state shown in FIG. The grease can be appropriately circulated on the sliding portion and the inner surface of the fixing film without being blocked.

(Example 2)
Next, FIGS. 5 and 6 are schematic views of an image forming apparatus according to the second embodiment.

  In this embodiment, the downstream step member 8a-6 is urged by the urging means 8a-7, and the eccentric cam 8a-8 is used as the protruding amount changing means for the fixing film 8a-1. As in the first embodiment, the amount of protrusion of the downstream step member to the fixing film is suppressed by an eccentric cam before the temperature rises, and applied to the sliding portion and the inner surface of the fixing film during rotation before temperature control before output. It is the structure which performs circulation of the done grease.

  Here, in FIGS. 5 and 6, the eccentric cam is housed in the film guide member 8a-2 in the fixing film 8a-1, but the eccentric cam is only a means for driving. For example, the eccentric cam is disposed outside the fixing film. It is also possible to change the amount of protrusion of the downstream step member provided on the other part via a lever or the like.

(Example 3)
Next, FIG. 7 shows a schematic diagram of an image forming apparatus according to the third embodiment.

  In this embodiment, the projecting amount changing means for the downstream step member 8a-6 to the fixing film 8a-1 is the piezoelectric element 8a-7, the input voltage to the piezoelectric element is controlled by the external voltage input means, and the downstream step member is It was set as the structure made to displace.

  In this configuration, since the control of the order of 10 μm is possible by the configuration of the piezoelectric element itself such as the laminated state and the configuration of the input voltage control means, the user alternately passes recording materials of different materials such as thickness. Therefore, it is possible to finely control the amount of protrusion of the downstream step according to a detection signal from a recording material thickness detection sensor (not shown) provided in the feeding section, and to minimize the load on the fixing film. is there.

  Further, as shown in FIG. 9 (fixing film etc. not shown), when a plurality of downstream step members 8a-6 and corresponding piezoelectric elements 8a-7 are arranged over the length of the film support means 8a-2, the paper is passed. The minimum downstream step means 8a-6 can be protruded with respect to the width L of the recording material S, so that the load on the fixing film can be minimized. Can be performed.

Example 4
Next, FIG. 8 shows a schematic view of an image forming apparatus according to the fourth embodiment.

  In this embodiment, the downstream step member 8a-6 is provided with an urging means 8a-7 so that the protruding load on the fixing film can be changed. In FIG. 8, the downstream step member and the biasing means are configured as separate members. However, the downstream step member is formed of an elastic member such as silicon rubber and the surface layer is subjected to a fluorine-based coating treatment. It is also possible to adopt a configuration having a variable function.

  In this configuration, for example, even when a recording material such as thick paper having a large basis weight and rigidity is passed, an increase in contact pressure between the inner surface of the fixing film and the downstream step member is avoided by the displacement or deformation of the downstream step. It is possible to prevent wear on the inner surface of the fixing film and to improve the durability of the fixing film base layer.

1 is a cross-sectional view of an electrophotographic color image forming apparatus showing a first embodiment of the present invention. Schematic diagram of the fixing nip of a conventional film-type fixing device 1 is a cross-sectional view of an electromagnetic heating type fixing device according to a first embodiment of the present invention (after temperature control). Sectional view of the electromagnetic heating type fixing device showing the first embodiment of the present invention (before temperature control) Sectional drawing (after temperature control) of the fixing device of the electromagnetic heating system which shows 2nd Example of this invention Sectional view (before temperature control) of an electromagnetic heating type fixing device showing a second embodiment of the present invention Sectional view of an electromagnetic heating type fixing device showing a third embodiment of the present invention Sectional view of an electromagnetic heating type fixing device showing a fourth embodiment of the present invention Schematic of an electromagnetic heating type fixing device showing a third embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 3 Scanner unit 4 Developing cartridge 5 Electrostatic transfer belt unit 7 Process cartridge 8 Fixing part 8a, b ... Fixing roller pair 17 Paper feed cassette 18 Paper feed roller 19 Registration roller pair 22 Adsorption roller 23a, b Paper discharge roller pair 24 discharge tray 100 color image forming apparatus S recording material

Claims (10)

A cylindrical film member, film support means for supporting the film member, a pressure member that pressurizes the film member to form a nip, and a sliding member that slides on the film member in the nip portion, In the heating means for nipping and conveying the recording material between the film member and the pressure member in the nip portion and fixing the image on the recording material,
In the vicinity of the nip, a step member that protrudes and bends the film member toward the pressure member from the sliding member is provided in the longitudinal direction of the film support member perpendicular to the recording material conveyance direction, and the step member protrudes to the film member. The quantity is variable.   The heating means according to claim 1, wherein the protruding amount of the step member is changed according to the temperature of the film support member or the pressure member.   The heating means according to claim 1 or 2, wherein the step member is supported by a bimetal or a shape memory alloy having a laminated structure of a plurality of metals having different coefficients of thermal expansion.   2. The heating means according to claim 1, wherein the step member is composed of an elastic member that is deformed by the rigidity of the recording material to be nipped and conveyed.   2. The heating unit according to claim 1, wherein the protruding amount of the step member is changed by a driving unit using a piezoelectric element.   The heating means according to claim 1, wherein the protruding amount of the step member is changed by a driving means using an eccentric cam.   The heating means according to claim 1, wherein the protruding amount of the step member is changed by a driving means using an electromagnet.   8. The heating means according to claim 1, wherein the protruding amount of the step member is changed by a signal of a recording material detection sensor disposed in the recording material conveyance path.   The heating means according to claim 8, wherein the recording material detection sensor is one of a paper thickness detection sensor, an OHT detection sensor, a gloss detection sensor, and a temperature / humidity sensor.   8. The heating means according to claim 1, wherein the protruding amount of the step member is changed within the recording material width detected by the width detection means of the recording material being conveyed.

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