JP2010217307A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of readily removing a recording medium caught between a separation member and a fixing member and preventing fluctuation of contact force of the separation member to the fixing member. <P>SOLUTION: The fixing device is provided with: the fixing member 31 which is heated by a heating means; a pressure member 34 which is arranged by contacting the fixing member 31; and the separation member 37, which is arranged so as to approach and separate to and from the surface of the fixing member 31 and is constituted so as to separate the recording medium, to which an image is fixed by the fixing member 31 and the pressure member 34 from the surface of the fixing member 31 by the separating member 37. The separating member 37 has a contact part 49, which contacts the surface of the fixing member 31. A magnet 50 is arranged in the contact part 49 and a magnetic body 51, which attracts the magnet 50 is arranged in the fixing member 31. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a fixing device that fixes an image on a recording medium and an image forming apparatus including the fixing device.

  2. Description of the Related Art Image forming apparatuses such as copiers, printers, facsimiles, and multi-function machines thereof often use a fixing device that fixes a toner image transferred onto a recording sheet as a recording medium by heat and pressure. The fixing device generally has a fixing member heated by a heating source and a pressure member pressed against the fixing member. By passing the recording paper on which the toner image has been transferred through a fixing nip formed by press-contacting the fixing member and the pressure member, the recording paper is heated and pressurized to fix the toner image on the recording paper.

  This type of heat fixing type fixing device melts toner on a recording sheet with heat during fixing. For this reason, particularly when an image with a high printing rate is printed, the melted toner on the recording paper adheres to the fixing member, which causes problems such as sticking of the recording paper to the fixing member and offset images. May occur. For this reason, in the conventional fixing device, a separation member formed in a claw shape or a plate shape is arranged to face the fixing member, and the recording sheet is separated from the fixing member by the separation member.

  Patent Document 1 below discloses a fixing device in which the separating member is urged toward the fixing member by a spring to improve the followability in order to stably bring the separating member into contact with the fixing member. .

  However, in the fixing device with improved followability, if the recording paper enters between the separation member and the fixing member and a paper jam occurs, the separation member is pushed by the jammed recording paper, and the separation member Is displaced in a direction away from the fixing member. As a result, the urging force of the spring increases, and there is a problem that it is difficult to remove the recording paper from between the separation member and the fixing member. Further, when the biasing force of the spring is increased, the load on the separating member and the fixing member is increased, and there is a possibility that these members are damaged.

  In order to solve the above problems, Patent Document 2 below proposes a fixing device having a mechanism for releasing the pressing of the fixing member against the fixing member. As shown in FIG. 18, the fixing device includes a separation claw 100 as a separation member, and a release arm 200 that releases the pressure of the separation claw 100 against the fixing member. The separation claw 100 is rotatably supported by the support shaft 300a of the frame 300. In addition, a spring 500 is stretched between the extended portion 400 extending from the separation claw 100 and the protruding portion 300 b provided on the frame 300. Under normal conditions, the tip of the separation claw 100 comes into contact with the fixing roller 600 as a fixing member by the biasing force (tensile force) of the spring 500. When the recording paper enters between the separation claw 100 and the fixing roller 600 and a paper jam occurs, the release arm 200 is rotated downward in the figure to contact the separation claw 100 and the separation claw 100 is moved. By rotating downward in the figure, the pressure applied to the fixing roller 600 by the separation claw 100 is released. Thereby, the workability of the paper jam removing operation is improved.

  Further, as shown in FIG. 19, in the above-mentioned Patent Document 2, a magnetic body 700 is provided in the separation claw 100 and a magnet 800 is provided in the release arm 200, and the magnetic attraction generated between the magnet 800 and the magnetic body 700 is used. There has been proposed a fixing device configured to bring the separation claw 100 into contact with the fixing roller 600. In this case, when the release arm 200 is rotated downward in the figure, the separation claw 100 is rotated downward together with the release arm 200 in a state of being magnetically attached to the magnet 800 of the release arm 200, and the separation claw 100 is fixed. The contact with the roller 600 can be released.

  By the way, a fixing member such as a fixing roller may be displaced by swinging in a direction approaching and separating from the separation member during driving. In the fixing device shown in FIG. 18, when the above-described vibration occurs when the fixing roller 600 rotates, or when the fixing roller 600 is rotated with the surface being uneven, the fixing roller 600 is rotated. Accordingly, the separation claw 100 is displaced, and the deformation amount (tensile amount or compression amount) of the spring 500 that biases the separation claw 100 is also changed, so that the contact force of the separation claw 100 with respect to the fixing roller 600 varies. In particular, when the fixing roller 600 is greatly displaced toward the separation claw 100, the biasing force of the spring 500 is increased and the contact force of the separation claw 100 is increased, so that the surface of the fixing roller 600 is damaged and an abnormal image is generated. There is a risk of doing. Further, when the contact force of the separation claw 100 with respect to the fixing roller 600 is increased, the separation claw 100 may be damaged.

  On the other hand, since the fixing device shown in FIG. 19 does not include a spring, there is no risk of damage to the member due to an increase in the biasing force of the spring. However, in the fixing device shown in FIG. 19, when the fixing roller 600 swings toward the separation claw 100 and the separation claw 100 is displaced along with this swing, the magnetic body 700 is displaced in a direction away from the magnet 800. There is a problem that the magnetic attraction is weakened. At this time, when the separation of the magnetic body 700 with respect to the magnetic attachment 800 becomes large and the magnetic attraction does not work completely, the separation claw 100 returns to the contact with the separation claw 100 while being separated from the fixing roller 600. It is also possible that it will not be possible. Further, if the magnetic attractive force between the magnet 800 and the magnetic body 700 is increased, the contact between the separation claw 100 and the fixing roller 600 can be prevented from being unexpectedly released, but the contact force increases. As a result, the separation claw 100 and the fixing roller 600 may be damaged.

  SUMMARY OF THE INVENTION In view of such circumstances, the present invention is intended to provide a fixing device capable of preventing fluctuations in the contact force of a separation member with respect to a fixing member, and an image forming apparatus including the fixing device.

  According to the first aspect of the present invention, the fixing member heated by the heating means, the pressure member disposed in contact with the fixing member, and the surface of the fixing member are disposed so as to approach and separate from each other. In the fixing device that includes a separation member and is configured to separate a recording medium on which an image has been fixed by the fixing member and the pressure member from the surface of the fixing member by the separation member, the separation member is a member of the fixing member. It has an abutting portion that abuts on the surface, and a magnet is disposed on one of the abutting portion and the fixing member, and a magnetic body or magnet attracting the magnet is disposed on the other.

  Usually, the separating member is arranged in a state of being in contact with the surface of the fixing member via a contact portion by a magnetic attractive force generated between the magnet and the magnetic body or between the magnets. In this state, the separation member can separate the recording medium on which the image is fixed by the fixing member and the pressure member from the surface of the fixing member. However, if the recording medium enters between the separation member and the fixing member and is sandwiched, the separation member is pushed by the sandwiched recording medium, so that the separation member is displaced away from the fixing member. . At this time, the magnet and the magnetic body or the magnets are separated from each other, and the magnetic attractive force generated between them is weakened, so that the urging force for bringing the separating member into contact with the fixing member is also weakened. Therefore, the fixing device according to the present invention does not increase the contact force of the separating member when the separating member is separated from the fixing member.

  Further, when the fixing member is displaced in the direction of approaching and separating from the separating member, the separating member is also displaced along with this displacement. At this time, since the relative distance between the magnet disposed on the contact portion of the separation member and the fixing member and the magnetic body or the magnets does not change, the magnetic attractive force generated between them does not change. Thereby, it is possible to maintain the contact force of the separating member with respect to the fixing member in a constant state.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, the abutting portion is disposed so as to abut on a surface of the fixing member excluding a recording medium passage region.

  As a result, it is possible to prevent the surface of the recording medium passage area of the fixing member from being damaged or worn, and to suppress problems such as the occurrence of abnormal images.

  According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the magnetic body is formed of a metal tape having an adhesive layer on the back surface.

  Thereby, a metal tape can be easily affixed on a fixing member. It is also possible to easily replace the attached metal tape.

  According to a fourth aspect of the present invention, in the fixing device according to the third aspect, the metal tape is attached to a contact surface with which the contact portion of the fixing member contacts.

  In this case, even if the metal tape is worn or deteriorated by contacting the contact portion or the magnet disposed on the metal tape, it can be easily replaced with a new metal tape. Furthermore, the relative distance between the separating member and the fixing member can be changed by changing the thickness of the metal tape. By changing the relative distance between the separation member and the fixing member, it is possible to adjust so that the separation effect of the recording medium by the separation member can be satisfactorily exhibited.

  According to a fifth aspect of the present invention, in the fixing device according to the third aspect, the metal tape is affixed to a surface opposite to a contact surface with which the contact portion of the fixing member contacts.

  In this case, since the contact portion or the magnet disposed on the metal tape does not contact the metal tape, wear and deterioration of the metal tape can be suppressed and the life can be extended. Further, in this case, since the metal tape is not attached to the contact surface of the fixing member, there is no possibility that the contact of the contact portion becomes unstable due to a dimensional error of the metal tape, a sticking accuracy error, or the like. Therefore, the contact portion can be stably brought into contact with the fixing member, and the relative distance of the separation member with respect to the fixing member can be maintained constant. Thereby, the separation effect of the recording medium by the separation member can be exhibited stably.

  According to a sixth aspect of the present invention, in the fixing device according to the first or second aspect, the fixing member is constituted by a plurality of layers laminated in a thickness direction, and the intermediate layer of the fixing member is used as the intermediate layer. It is a metal layer as a magnetic material.

  Also in this case, since the contact portion, the magnet disposed on the metal layer, and the like do not contact the metal layer, wear and deterioration of the metal layer can be suppressed to extend the life. Further, when the magnetic material is constituted by the metal layer, there is no possibility of peeling off from the fixing member during use, such as a metal tape. Further, in this case, since the metal tape is not attached to the contact surface of the fixing member, there is no possibility that the contact of the contact portion becomes unstable due to a dimensional error of the metal tape, a sticking accuracy error, or the like. Therefore, the contact portion can be stably brought into contact with the fixing member, and the relative distance of the separation member with respect to the fixing member can be maintained constant. Thereby, the separation effect of the recording medium by the separation member can be exhibited stably.

  A seventh aspect of the invention is the fixing device according to any one of the first to sixth aspects, wherein the separating member is disposed above the fixing member.

  When the separating member is disposed above the fixing member, the separating member spaced upward with respect to the fixing member can be brought close to the fixing member by its own weight and returned to the original contact state.

  According to an eighth aspect of the present invention, in the fixing device according to any one of the first to seventh aspects, an auxiliary spring that urges the separating member in a direction to approach the fixing member is provided.

  When the auxiliary spring for biasing the separation member is provided, the separation member separated from the fixing member can be reliably returned to the original contact state by the auxiliary spring. If there is a possibility that the contact force of the separation member cannot be sufficiently secured only by the magnetic attractive force generated between the magnet and the magnetic body or between the magnets, the separation member can be separated by assisting the contact of the separation member with an auxiliary spring. Sufficient contact force of the member can be ensured.

  A ninth aspect of the invention is an image forming apparatus including the fixing device according to any one of the first to eighth aspects.

  The fixing device of the present invention can be mounted on an image forming apparatus.

  According to the present invention, when a recording medium is sandwiched between the separation member and the fixing member and the separation member is displaced in a direction away from the fixing member, the separation occurs between the magnet and the magnetic body or between the magnets. Since the magnetic attractive force becomes weak, the contact force of the separation member can be reduced. Thereby, the recording medium sandwiched between the fixing member and the separating member can be easily removed.

  In addition, according to the present invention, even when the fixing member is displaced in the direction of approaching and separating from the separation member, the abutting portion of the separation member and the magnet disposed on the fixing member and the magnetic body or the magnets are relatively Since the distance does not change, the contact force of the separating member with respect to the fixing member can be maintained in a constant state. Accordingly, it is possible to prevent the contact force of the separation member from increasing, and it is possible to suppress damage to the fixing member or the separation member. In addition, since the separation member can be prevented from being separated unexpectedly due to a decrease in the contact force of the separation member, the separation effect can be stably exhibited and the reliability can be improved.

1 is a schematic configuration diagram of a monochrome image forming apparatus equipped with a fixing device according to the present invention. 1 is a schematic configuration diagram of a fixing device according to the present invention. FIG. 3 is a side view illustrating a main part of the fixing device according to the first exemplary embodiment of the present invention. It is a perspective view of the principal part shown in FIG. It is a side view which shows the principal part of the fixing device which concerns on Example 2 of this invention. FIG. 9 is a side view illustrating a main part of a fixing device according to a third embodiment of the present invention. FIG. 7 is an enlarged cross-sectional view of the fixing belt shown in FIG. 6. FIG. 10 is a side view illustrating a main part of a fixing device according to Embodiment 4 of the present invention. It is a perspective view which shows the principal part of the fixing device which concerns on Example 5 of this invention. 1 is a schematic configuration diagram of a fixing device having a fixing pad. 1 is a schematic configuration diagram of a fixing device in which a fixing nip is formed by a fixing belt and a pressure belt. FIG. 3 is a schematic configuration diagram of a fixing device in which a fixing nip is formed by a fixing sleeve and a pressure roller. 1 is a schematic configuration diagram of a fixing device in which a fixing nip is formed by a fixing roller and a pressure roller. 1 is a schematic configuration diagram of a fixing device in which a fixing nip is formed by a fixing roller and a pressure belt. 1 is a schematic configuration diagram of a color image forming apparatus according to the present invention. FIG. 3 is a diagram illustrating a normal operation state in the fixing device according to the present invention. FIG. 6 is a diagram illustrating a state when a paper jam occurs in the fixing device according to the present invention. It is a schematic block diagram of the conventional fixing device. It is a schematic block diagram of another conventional fixing device.

FIG. 1 is a schematic configuration diagram of a monochrome image forming apparatus according to the present invention.
The image forming apparatus illustrated in FIG. 1 includes a process unit 1 as an image forming unit configured to be detachable from the image forming apparatus main body H. The process unit 1 includes a photosensitive member 2 as an electrostatic latent image carrier, a charging roller 3 as a charging unit that charges the surface of the photosensitive member 2, and a developing unit that forms a toner image on the surface of the photosensitive member 2. A developing device 4 and a cleaning blade 5 as a cleaning unit for cleaning the surface of the photoreceptor 2 are provided.

  The image forming apparatus also includes an exposure device 7 that forms an electrostatic latent image on the surface of each photoconductor 2 and a transfer device 6 that transfers a toner image formed on the surface of the photoconductor 2 onto a recording sheet as a recording medium. A fixing device 8 (fixing unit) for fixing the image on the recording paper, and a paper feeding unit 9 for supplying the recording paper.

  The paper feed unit 9 includes a plurality of paper feed cassettes 10 and 11 that store the recording paper P, and paper feed rollers 12 and 13 that carry the recording paper P out of the paper feed cassettes 10 and 11. In the image forming apparatus main body H, a conveyance path R for guiding the recording paper P from the paper supply unit 9 to the paper discharge tray 16 at the upper part of the apparatus is disposed. A pair of registration rollers 14 is disposed on the upstream side in the transport direction of the transfer device 6 in the transport path R, and a pair of paper discharge rollers 15 is disposed at the downstream end of the transport path R in the transport direction.

The basic operation of the image forming apparatus will be described below with reference to FIG.
The photosensitive member 2 is rotated in the direction of the arrow in the figure, and the surface of the photosensitive member 2 is charged to a uniform high potential by the charging roller 3. Next, the surface of the photosensitive member 2 is irradiated with the laser beam L from the exposure device 7 based on the image data, and the potential of the irradiated portion is lowered to form an electrostatic latent image. The toner charged by the developing device 4 is electrostatically transferred to the portion of the electrostatic latent image formed on the surface of the photoreceptor 2 to form a toner image (visualization).

  Further, the recording paper P is sent out to the transport path R by a paper feed roller 12 or 13 from one of the paper feed cassettes 10 and 11. The fed recording paper P is temporarily stopped by the registration roller 14. Thereafter, the driving of the registration roller 14 is resumed, and the recording paper P is conveyed to the transfer device 6 in synchronism with the toner image on the photoreceptor 2. The toner image on the photoreceptor 2 is transferred to the recording paper P by the transfer device 6, and the recording paper P is sent to the fixing device 8. Then, the recording paper P is heated and pressurized by the fixing device 8, and the toner image is fixed on the recording paper P. The recording paper P on which the toner image is fixed is discharged to a paper discharge tray 16 by a paper discharge roller 15.

  Further, the toner remaining on the surface of the photoreceptor 2 after the transfer process is removed by the cleaning blade 5, and the surface of the photoreceptor 2 is neutralized by a neutralizing lamp (not shown).

Next, the configuration of the fixing device 8 mounted on the image forming apparatus will be described with reference to FIG.
As shown in FIG. 2, the fixing device 8 mainly includes a fixing roller 30, a fixing belt 31, a heating roller 32, an induction heating unit 33, a pressure row 34, a thermostat 35, a guide plate 36, a separation member 37, and the like. The This fixing device has a configuration in which the temperature can be raised for a short time to reach the fixing possible temperature in about 20 to 30 seconds using IH heating, and 30 to 50 sheets can be printed per minute. It has become.

  The fixing roller 30 has an outer diameter of 30 to 50 mm, and a highly heat-insulating elastic layer 30b such as foamed silicon rubber is formed on the surface of an aluminum, stainless steel (SUS), or iron core 30a with a thickness of 2 to 15 mm. Has been. The fixing roller 30 is driven to rotate counterclockwise in FIG. 2 by a driving unit (not shown). By using foamed silicon rubber for the elastic layer 30b, it is possible to reduce the thermal conductivity, to prevent the heat transfer from the fixing belt 31, and to reduce the apparent heat capacity.

  The heating roller 32 is a cylindrical body having an outer diameter of 15 to 25 mm and made of a nonmagnetic material such as SUS304 (stainless steel) and having a thickness of 300 to 1000 μm, and rotates counterclockwise in the figure. An inner core 32a (core portion) made of a ferromagnetic material such as ferrite is installed inside the heating roller 32, and a copper plating layer is formed on the surface of stainless steel between the fixing belt 31 and the inner core 32a. The heat generation layer 32b is disposed. As will be described later, the heat generating layer 32b generates an eddy current when receiving an alternating magnetic field, and generates a Joule heat by the eddy current to heat the fixing belt 31 stretched thereon. . The heat generation layer 32b is not limited to a copper-plated layer formed on the surface of stainless steel, but a magnetic metal material such as iron, cobalt, nickel, or an alloy thereof, polyimide resin, or the like, such as copper or aluminum. A plated layer of a good conductor may be formed. The inner core 32 a as a core part is opposed to the coil part 38 of the induction heating part 33 with the fixing belt 31 interposed therebetween. By ensuring the strength and reducing the thickness of the heating roller 32, the heat capacity can be reduced and the temperature can be raised to a desired temperature in a short time.

  The fixing belt 31 is an endless belt having an outer diameter of 50 to 80 mm, and is stretched and supported by the heating roller 32 and the fixing roller 30. The fixing belt 31 has a base layer made of a polyimide resin having a thickness of 50 to 200 μm provided with an elastic layer such as a silicon rubber of 70 to 300 μm, and a release layer made of a fluorine compound or the like with a thickness of 5 to 50 μm on the surface layer. A layer (surface layer) is provided to form an endless belt having a multilayer structure. The release property of the toner image T is ensured by the release layer of the fixing belt 31.

  The induction heating unit 33 includes a coil unit 38, a core 39, a side core 40, a core unit including a center core 41, a coil guide 42, and the like. Here, the coil unit 38 extends a litz wire in which fine wires are bundled in the width direction (in the direction perpendicular to the paper in FIG. 2) so as to cover a part of the fixing belt 31 wound around the heating roller 32. It is a thing. The coil guide 42 is made of a resin material having high heat resistance and holds the coil portion 38, the core 39, the side core 40, and the center core 41. The core 39, the side core 40, and the center core 41 are all made of a material having high magnetic permeability such as ferrite. The core 39 is installed so as to face the coil portion 38 extending in the width direction. The side core 40 is installed at the end of the coil portion 38. The center core 41 is installed at the center of the coil portion 38, and a litz wire is wound around the center core 41 to form the coil portion 38.

  The “core portion” of the fixing device 8 refers to both opposing core portions that contribute to electromagnetic induction heating. Therefore, the core part of the fixing device 8 is the core 39, the side core 40, the center core 41 of the induction heating part 33, and the internal core 32 a provided inside the heating roller 32. By installing the inner core 32a in the heating roller 32, a good magnetic field is formed between the core 39 and the inner core 32a, and the heating roller 32 and the fixing belt 31 can be efficiently heated. That is, the “core portion” of the fixing device 8 functions as a heating unit that heats the fixing belt as a fixing member.

  The pressure roller 34 has a diameter of 30 to 50 mm, and an elastic layer 34b of 1 to 10 mm of fluorine rubber or silicon rubber or the like is formed on a core metal 34a of Fe, Al, SUS (stainless steel) or the like. The outer layer is composed of a release layer 34c made of a fluorine compound or the like with a thickness of 5 to 50 μm. The pressure roller 34 is in pressure contact (contact) with the fixing roller 30 via the fixing belt 31 to form a fixing nip N.

  A guide plate 36 for guiding the recording paper P is disposed on the entrance side of the contact portion (fixing nip N) between the fixing belt 31 and the pressure roller 34. A separation member 37 that guides the recording paper P and separates the recording paper P from the fixing belt 31 is disposed on the exit side of the contact portion (fixing nip N) between the fixing belt 31 and the pressure roller 34. .

  A thermostat 35 is in contact with a part of the outer peripheral surface of the heating roller 32. When the temperature of the heating roller 32 detected by the thermostat 35 exceeds a predetermined temperature, the thermostat 35 cuts off the energization to the induction heating unit 33 and stops the heating of the fixing belt 31 by the induction heating unit 33. Although not shown in the figure, a thermistor as a temperature detecting means is installed on the fixing belt 31, and the surface temperature on the fixing belt 31 is directly detected to control the temperature. As the temperature detecting means, a thermopile that detects the temperature of the fixing belt 31 in a non-contact manner can also be used. The fixing device 8 configured as described above operates as follows.

  First, reload control for heating the fixing belt 31 to a preset temperature threshold (hereinafter, referred to as a fixing temperature) so as to enable a fixing process is started. Specifically, the fixing belt 31 rotates (rotates) in the direction of the arrow in FIG. 2 as the fixing roller 30 rotates, and the heating roller 32 rotates in the counterclockwise direction in FIG. At the same time, the pressure roller 34 also rotates in the direction of the arrow in FIG. The fixing belt 31 is heated by the induction heating unit 33 that is energized. Specifically, the magnetic field lines are alternately switched between the core 39 and the inner core 32a by passing a high-frequency alternating current through the coil portion 38. At this time, an eddy current is generated on the surface of the heat generating layer 32b of the heating roller 32, and Joule heat is generated by the electric resistance of the heat generating layer 32b. The fixing belt 31 wound around the heating roller 32 is heated by the Joule heat. The temperature of the fixing belt 31 is detected by a thermistor, and it is determined whether or not the temperature of the fixing belt 31 has reached the fixing temperature based on the detected temperature.

  When the temperature of the fixing belt 31 reaches the fixing temperature and reloading is completed, the recording paper P onto which the toner image T has been transferred enters the fixing nip N, and the toner image T on the paper P is heated in the fixing nip N. Melt. Specifically, the recording paper P carrying the toner image T through the image forming process described above is fed into the fixing nip N between the fixing belt 31 and the pressure roller 34 while being guided by the guide plate 36. . The toner image T is fixed to the recording paper P by the heat received from the fixing belt 31 and the pressure received from the pressure roller 34, and the recording paper P is sent out between the fixing belt 31 and the pressure roller 34.

  Hereafter, the characteristic part of this invention is demonstrated.

Hereinafter, the configuration of the fixing device according to the first exemplary embodiment of the present invention will be described with reference to FIGS. 3 and 4. 3 is a side view showing the main part of the fixing device 8, and FIG. 4 is a perspective view of the main part. Moreover, in FIG. 3 and FIG. 4, the same code | symbol has shown the same member.
As shown in FIG. 3, the separation member 37 is rotatably attached to a support shaft 43 (support member) provided in the main body of the fixing device 8 or the image forming apparatus main body. The separation member 37 is configured to approach and separate from the surface of the fixing belt 31 by rotating the separation member 37 around the support shaft 43.

  As shown in FIG. 4, the separation member 37 has a frame 44 extending in the width direction of the fixing belt 31 and a separation claw 45 disposed on the frame 44. A plurality of separation claws 45 are arranged side by side in the longitudinal direction of the frame 44, and each separation claw 45 is attached to the frame 44 via a holder 46. At both ends of the frame 44, there are provided substantially C-shaped arm portions 48 in which shaft holes 47 for inserting the support shafts 43 (not shown) are formed. Further, contact portions 49 that can contact the surface of the fixing belt 31 are disposed on both ends of the frame 44. Specifically, the abutting portion 49 is disposed so as to abut on the surfaces of both ends of the fixing belt 31 excluding the recording medium passage area A.

  A rectangular magnet 50 (permanent magnet) is disposed on the surface (contact surface) that contacts the fixing belt 31 of the contact portion 49. On the other hand, a metal tape 51 as a magnetic material is disposed on the entire surface (contact surface) on both ends of the fixing belt 31 with which the contact portion 49 contacts. As described above, by arranging the magnet 50 and the metal tape 51 to correspond to each other, the contact portion 49 contacts the surface of the fixing belt 31 due to the magnetic attraction generated between the magnet 50 and the metal tape 51. It is to be held in the state.

  The metal tape 51 has an adhesive layer on the back surface. The metal tape 51 is attached to the surface of the fixing belt 31 by the adhesive force of the adhesive layer. Therefore, the metal tape 51 can be easily attached to and detached from the fixing belt 31. The width of the metal tape 51 is set to be equal to or larger than the width of the magnet 50.

FIG. 5 shows a main part of the fixing device 8 according to the second embodiment of the present invention. In FIG. 5, the same reference numerals as those in FIG. 3 or 4 indicate the same members.
As shown in FIG. 5, in the fixing device 8 according to the second embodiment, similarly to the fixing device according to the first embodiment of the present invention, the magnet 50 is disposed at the contact portion 49 of the separation member 37, and the magnet A metal tape 51 is attached to the fixing belt 31 so as to correspond to 50. However, here, the metal tape 51 is affixed to the back surface of the fixing belt 31 (the surface opposite to the contact surface that contacts the contact portion 49). Since the other configuration is the same as that of the first embodiment of the present invention, the description thereof is omitted.

FIG. 6 shows a main part of the fixing device 8 according to the third embodiment of the present invention. In FIG. 6, the same reference numerals as those in FIG. 3 or 4 indicate the same members.
As shown in FIG. 6, the fixing device 8 according to the third embodiment also includes a magnet 50 at the contact portion 49 of the separation member 37, as in the fixing device according to each of the embodiments of the present invention. In addition, a metal layer 52 as a magnetic body is disposed in the fixing belt 31 at a location corresponding to the magnet 50. Specifically, as shown in FIG. 7, the fixing belt 31 is provided on the inner peripheral surface side base layer 53, the metal layer 52 provided on the base material layer 53, and the metal layer 52. The elastic layer 54 and the release layer 55 on the outer peripheral surface disposed on the elastic layer 54 are configured. In this case, since the metal layer 52 is disposed only at a position corresponding to the magnet 50 within the width of the fixing belt 31, the base layer 52 is formed thick at a position where the metal layer 52 is not disposed. . The configuration of the fixing belt 31 is not limited to the configuration shown in FIG. The metal layer 52 may be an intermediate layer of the fixing belt 31 constituted by a plurality of layers. Since the other configuration is the same as that of the first embodiment of the present invention, the description thereof is omitted.

FIG. 8 shows a main part of the fixing device 8 according to the fourth embodiment of the present invention. In FIG. 8, the same reference numerals as those in FIG. 3 or FIG. 4 indicate the same members.
The fixing device 8 according to the fourth embodiment shown in FIG. 8 is basically configured similarly to the first embodiment. Further, the fixing device 8 according to the fourth embodiment includes an auxiliary spring 56 that urges the separation member 37 in a direction in which the separation member 37 approaches the fixing belt 31. The auxiliary spring 56 is merely for providing an auxiliary biasing force to the separation member 37, and the contact portion 49 of the separation member 37 is brought into contact with the fixing belt 31 only by the biasing force of the auxiliary spring 56. It is not designed to be held in a state. In this case as well, the contact portion 49 is held in contact with the surface of the fixing belt 31 by the magnetic attraction generated between the magnet 50 and the metal tape 51, as in the embodiments of the present invention. .

  In FIG. 8, the metal tape 51 is disposed on the surface (contact surface) of the fixing belt 31, but the metal tape 51 is disposed on the back surface (surface opposite to the contact surface) of the fixing belt 31. May be. Alternatively, the intermediate layer of the fixing belt 31 may be a metal layer.

  FIG. 9 shows a fixing device according to Embodiment 5 of the present invention. 9, the same reference numerals as those in FIG. 4 denote the same members as in FIG. 4, but the separation member 37 according to the fifth embodiment does not include the separation claw 45 and the holder 46 shown in FIG. In this case, the member denoted by reference numeral 44 in FIG. 9 functions as a separation plate. The other configuration of the fifth embodiment is the same as that of the first embodiment shown in FIG. Thus, the configuration of the present invention can also be applied to a fixing device including the separation member 37 that does not have the separation claw 45 or the like. Further, one or a plurality of configurations can be appropriately selected from the configurations of the above-described Examples 2 to 4 and applied to the fixing device illustrated in FIG.

  In each of the embodiments of the present invention, the separation member 37 is provided with the magnet 50 and the fixing belt 31 is provided with the magnetic metal tape 51. On the contrary, the separation member 37 is provided with a metal tape or the like. Alternatively, a magnet may be provided on the fixing belt 31. It is also possible to arrange magnets that attract each other on the separating member 37 and the fixing belt 31.

  The fixing device according to each of the above embodiments includes a fixing belt 31 as a rotatable fixing member (fixing rotator), a pressure roller 34 as a rotatable pressure member (pressure rotator), and a fixing. Although the induction heating unit 33 and the heating roller 32 are provided as heating means for heating the member, the fixing member, the pressure member, the heating means, and the like are not limited to those described above. For example, the configuration of the present invention can be applied to a fixing device described below.

  The fixing device shown in FIG. 10 includes a heating roller 62 including a heater 61, a fixing pad 63, a fixing belt 64 serving as a fixing rotating member stretched over the fixing pad 63 and the heating roller 62, and a heater 65. A pressure roller 66 as a pressure rotating body is provided. The pressure roller 66 is in contact with the fixing belt 64 with a predetermined pressure at a position facing the fixing pad 63. When the fixing process is performed by the fixing device, the two heaters 61 and 65 are heated to heat the fixing belt 64 and the pressure roller 66, and the fixing belt 64 and the fixing belt 64 reach the fixing temperature. By passing the recording paper P on which the unfixed toner image T is formed through a pressure contact portion (fixing nip) with the pressure roller 66, the recording paper P is heated and pressed to fix the toner image T.

  The fixing device shown in FIG. 11 includes a fixing belt 70 as a fixing rotating body that is stretched around a plurality of rollers 67 and 68 and a guide member 69, and a pressure that is stretched around the rollers 71 and 72 and the guide member 73. A pressure belt 74 as a rotating body is provided. The pressure belt 74 is in contact with the fixing belt 70 by a roller 71 at a predetermined pressure. The rollers 67 and 71 have heaters 75 and 76 as heating means, respectively. When the fixing process is performed by the fixing device, the two heaters 75 and 76 are heated to heat the fixing belt 70 and the pressure belt 74, and the fixing belt 64 and the fixing belt 64 reach the fixing temperature. By passing the recording paper P on which the unfixed toner image T is formed through a pressure contact portion (fixing nip) with the pressure belt 74, the recording paper P is heated and pressurized to fix the toner image T.

  The fixing device shown in FIG. 12 has a flexible endless belt-like fixing sleeve 77 as a fixing rotating body, a heater 79 as a heating means for heating the fixing sleeve 77, and a heater holder 80 for holding the heater 79. And a pressure roller 78 as a pressure rotator. When the fixing process is performed by the fixing device, the heater 79 generates heat to heat the fixing sleeve 77 and the fixing sleeve 77 reaches the fixing temperature, and the pressure contact portion (fixing) between the fixing sleeve 77 and the pressure roller 78 is fixed. The recording paper P on which the unfixed toner image T is formed is passed through the nip), whereby the recording paper P is heated and pressed to fix the toner image T.

  13 heats the fixing roller 81 as a fixing rotator, the pressure roller 82 as a pressure rotator disposed in pressure contact with the fixing roller 81, and the fixing roller 81. A heater 83 as a heating means is provided. When the fixing process is performed by the fixing device, the fixing roller 81 and the pressure roller 82 are heated with the heater 83 heated to heat the fixing roller 81 and the pressure roller 82, and the fixing roller 81 reaches the fixing temperature. The recording paper P on which the unfixed toner image T is formed is passed through the pressure contact portion (fixing nip), and the recording paper P is heated and pressurized to fix the toner image T.

  The fixing device shown in FIG. 14 includes a fixing roller 84 as a fixing rotator, a heater 87 as a heating means for heating the fixing roller 84, an endless pressure belt 85 as a pressure rotator, and a pressure belt. A pressure pad 86 or the like is provided to bring 85 into contact with the fixing roller 84 with a predetermined pressure. When the fixing process is performed by this fixing device, the heater 87 generates heat to heat the fixing roller 84, and the fixing roller 84 reaches the fixing temperature, and the pressure contact portion (fixing) between the fixing roller 84 and the pressure belt 85 is fixed. The recording paper P on which the unfixed toner image T is formed is passed through the nip), whereby the recording paper P is heated and pressed to fix the toner image T.

  In each of the fixing devices described with reference to FIGS. 10 to 14, a separating member that approaches and separates from a fixing rotator (fixing member) such as a fixing belt, a fixing sleeve, or a fixing roller is provided. It is possible to arrange a magnet on either one of them and a magnetic body or magnet attracting the magnet on the other.

  Further, the fixing device according to the present invention can be mounted not only on the monochrome image forming apparatus shown in FIG. 1 but also on the color image forming apparatus shown in FIG. FIG. 15 is a schematic configuration diagram of a color image forming apparatus equipped with the fixing device of the present invention. The image forming apparatus shown in FIG. 15 includes four process units 1Y, 1C, 1M, and 1Bk as a plurality of image forming units that form images of different colors. Each of the process units 1Y, 1C, 1M, and 1Bk includes a photosensitive member 20 as an image carrier, a charging roller 21 as a charging unit that charges the surface of the photosensitive member 20, and a developing that supplies toner to the surface of the photosensitive member 20. The image forming apparatus main body H is configured to include a developing device 22 as a means and a cleaning blade 23 as a cleaning means for cleaning the surface of the photoreceptor 20.

  The image forming apparatus also includes an exposure device 24 as an exposure unit that exposes the surface of each photoconductor 20, a transfer device having an intermediate transfer belt 25 and the like, a paper feed cassette 26 that stores recording paper P, and the like. A sheet feeding unit and a fixing device 27 (fixing unit) are provided. Here, the fixing device according to the present invention can be applied as the fixing device 27. Four primary transfer rollers 18 as primary transfer means are disposed on the inner peripheral surface of the intermediate transfer belt 25. A secondary transfer roller 19 as a secondary transfer unit is disposed on the outer peripheral surface of the intermediate transfer belt 25.

The basic operation of the image forming apparatus shown in FIG. 15 will be described below.
When the image forming operation is started, the photoconductors 20 of the process units 1Y, 1C, 1M, and 1Bk are rotationally driven clockwise by a driving device (not shown), and the surface of each photoconductor 20 is predetermined by the charging roller 21. It is uniformly charged to the polarity. The surface of each charged photoconductor 20 is irradiated with laser light from the exposure device 24, and an electrostatic latent image is formed on the surface of each photoconductor 20. At this time, the image information exposed to each photoconductor 20 is single-color image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. The electrostatic latent image formed on the photoconductor 20 in this manner is supplied with toner by each developing device 22 so that the electrostatic latent image is visualized as a toner image.

  The intermediate transfer belt 25 is driven to run in the direction indicated by the arrow in the drawing, and the toner images of the respective colors formed on the respective photoconductors 20 are sequentially superimposed and transferred onto the intermediate transfer belt 25 at the position of the primary transfer roller 18. Thus, the intermediate transfer belt 25 carries a full-color toner image on its surface.

  Further, the recording paper P is sent out from the paper feed cassette 26 in timing with the toner image on the intermediate transfer belt 25. Then, the toner images on the intermediate transfer belt 25 are collectively transferred onto the recording paper P at the position of the secondary transfer roller 19. The recording paper P onto which the toner image has been transferred is conveyed to the fixing means 27, and the toner image is fixed by applying heat and pressure to the recording paper P by the fixing roller 28 and the pressure roller 29. The recording paper P on which the toner image is fixed is discharged to a stock unit outside the apparatus.

  The above description is an image forming operation when a full color image is formed. A single color image is formed using any one of the four process units 1Y, 1C, 1M, and 1Bk, or two or three. It is also possible to use two process units to form a two-color or three-color image.

  Further, the image forming apparatus according to the present invention is not limited to the monochrome image forming apparatus shown in FIG. 1 or the color image forming apparatus shown in FIG. 15, but other copiers, printers, facsimiles, or complex machines thereof. It may be.

Hereinafter, the operation and effect of the separation member 37 which is a characteristic part of the present invention will be described.
First, operations and effects common to the embodiments of the present invention will be described with reference to FIGS. 16 and 17. 16 and 17, the same reference numerals as those in FIG. 3 denote the same members. As shown in FIG. 16, the separating member 37 normally has the fixing belt 31 of the fixing belt 31 by a magnetic attraction generated between the magnet 50 provided in the contact portion 49 and the metal tape 51 provided in the fixing belt 31. It arrange | positions in the state contact | abutted on the surface. Further, in this state, the separation claw 45 (see FIG. 4) provided on the separation member 37 is held in a non-contact state via a preset gap with respect to the surface of the fixing belt 31. Then, the recording paper P on which the unfixed image is formed is passed through the fixing nip N formed by the fixing belt 31 and the pressure roller 34 being pressed against each other, and the image is fixed. The recording paper P is separated from the surface of the fixing belt 31 by the separation claw 45 and conveyed upward in the drawing. In the embodiment shown in FIG. 9, the recording paper P is separated from the fixing belt 31 by the separation plate 44 instead of the separation claw 45.

  However, as shown in FIG. 17, when the recording paper P enters between the separation claw 45 (not shown) or the frame 44 (the separation plate 44 in FIG. 9) and the fixing belt 31 and a paper jam occurs, the separation claw 45 or the like When the separation claw 45 and the like are pushed by the jammed recording paper P sandwiched between the fixing belt 31 and the fixing belt 31, the entire separation member 37 is displaced (rotated) in a direction away from the fixing belt 31. At this time, when the separating member 37 is displaced in a direction away from the fixing belt 31, the magnet 50 magnetically attached to the metal tape 51 on the fixing belt 31 is also separated. When the magnet 50 and the metal tape 51 are separated from each other, the magnetic attractive force generated between the magnet 50 and the metal tape 51 is weakened, so that the contact force of the separation member 37 to the fixing belt 31 is also reduced. That is, unlike the conventional fixing device that biases the separation member by a spring, the fixing device according to the present invention increases the contact force of the separation member 37 by separating the separation member 37 from the fixing belt 31. Absent. Therefore, according to the fixing device of the present invention, the recording paper P sandwiched between the fixing belt 31 and the separating member 37 can be easily removed.

  Further, when the fixing belt 31 is shaken during driving and the fixing belt 31 is displaced in the direction of approaching and separating from the separating member 37, the separating member 37 is also displaced (rotated) along with this displacement. The magnet 50 disposed on 49 and the metal tape 51 disposed on the fixing belt 31 are held in a state of being magnetically attached to each other. At this time, since the relative distance between the magnet 50 and the metal tape 51 does not change, the magnetic attractive force generated between them does not change. Therefore, the contact force of the separating member 37 does not change, and the contact force can be maintained in a constant state. As a result, damage to the fixing belt 31 or the separation member 37 due to an increase in the contact force of the separation member 37 can be suppressed. On the other hand, since the separation member 37 can be prevented from being separated from the fixing belt 31 due to the contact force of the separation member 37 being reduced, the separation effect of the recording paper by the separation member 37 can be stably exhibited. Is possible.

  In each embodiment of the present invention, since the separating member 37 is disposed above the fixing belt 31, after the jammed recording paper P is removed, the separating member 37 rotates downward by its own weight, and the magnet When 50 is magnetically attached to the metal tape 51, the separation member 37 is held in its original contact state.

  When the auxiliary spring 56 that biases the separation member 37 is provided as in the embodiment shown in FIG. 8, the separation member 37 separated from the fixing belt 31 is reliably returned to the original contact state by the auxiliary spring 56. It is possible to make it. When there is a possibility that the contact force of the separation member 37 cannot be sufficiently secured only by the magnetic attraction force by the magnet 50, the contact force of the separation member 37 is increased by assisting the contact of the separation member 37 by the auxiliary spring 56. It can be secured sufficiently. The auxiliary spring 56 is only for providing an auxiliary biasing force to the separating member 37, and therefore is a case where the separating member 37 is separated from the fixing belt 31 due to a paper jam. However, there is no possibility that the contact force of the separating member 37 increases so as to make it difficult to remove the jammed recording paper.

  In the fixing device according to each embodiment of the present invention, the contact portion 49 of the separation member 37 is disposed so as to contact the surface of the fixing belt 31 except the recording medium passage area A (see FIG. 4). ). As a result, the surface of the recording medium passage area A of the fixing belt 31 can be prevented from being damaged or worn, and problems such as the occurrence of abnormal images can be suppressed.

  Further, when the metal tape 51 is affixed to the surface of the fixing belt 31, even if the metal tape 51 is abraded or deteriorated due to contact of the magnet 50 or the like with the metal tape 51, it can be easily combined with the new metal tape 51. Can be exchanged. Furthermore, the relative distance (gap) between the separating member 37 and the fixing belt 31 can be changed by changing the thickness of the metal tape 51. By changing the relative distance (gap) between the separation member 37 and the fixing belt 31, it is possible to adjust so that the separation effect of the recording paper by the separation member 37 can be satisfactorily exhibited.

  On the other hand, when the metal tape 51 is affixed to the back surface of the fixing belt 31, the magnet 50 does not come into contact with the metal tape 51, so that the wear and deterioration of the metal tape 51 are suppressed to extend the life. Can do. In this case, since the metal tape 51 is not attached to the surface of the fixing belt 31, there is no possibility that the contact of the contact portion 49 becomes unstable due to a dimensional error of the metal tape 51, a sticking accuracy error, or the like. Therefore, the contact portion 49 can be stably brought into contact with the surface of the fixing belt 31, and the relative distance (gap) of the separation member 37 with respect to the fixing belt 31 can be maintained constant. Thereby, the separation effect of the recording paper by the separation member 37 can be stably exhibited.

  When the intermediate layer of the fixing belt 31 is composed of the metal layer 52, the magnet 50 or the like does not come into contact with the metal layer 52, so that wear and deterioration of the metal layer 52 can be suppressed and the life can be extended. Further, in this case, unlike the metal tape 51, there is no possibility of peeling from the fixing belt 31 during use. Further, in this case, there is no possibility that the contact of the contact portion 49 becomes unstable due to a dimensional error or a pasting accuracy error of the metal tape 51. Accordingly, since the contact portion 49 can be stably brought into contact with the fixing belt 31, the separation effect of the recording medium by the separation member 37 can be stably exhibited.

  Although the operation and effect of each embodiment of the present invention has been described above, the above configuration is also applicable when the configuration of the present invention is applied to any of the fixing devices shown in FIGS. 10 to 14 or the color image forming apparatus shown in FIG. The same actions and effects can be achieved.

8 Fixing Device 30 Fixing Roller 31 Fixing Belt 34 Pressing Roller 37 Separating Member 49 Contacting Part 50 Magnet 51 Metal Tape 52 Metal Layer 56 Auxiliary Spring A Recording Medium Passing Area N Fixing Nip P Recording Paper

JP 2006-11193 A JP-A-11-174890

Claims (9)

A fixing member heated by a heating unit; a pressure member disposed in contact with the fixing member; and a separation member disposed so as to approach and separate from the surface of the fixing member. In a fixing device configured to separate a recording medium on which an image is fixed by a member and the pressure member from a surface of the fixing member by the separation member,
The separation member has a contact portion that contacts the surface of the fixing member, and a magnet is disposed on one of the contact portion and the fixing member, and a magnetic body or magnet attracting the magnet is disposed on the other. A fixing device characterized by being arranged.   The fixing device according to claim 1, wherein the abutting portion is disposed so as to abut on a surface of the fixing member excluding a recording medium passage region.   The fixing device according to claim 1, wherein the magnetic body is formed of a metal tape having an adhesive layer on the back surface.   The fixing device according to claim 3, wherein the metal tape is attached to a contact surface with which the contact portion of the fixing member contacts.   The fixing device according to claim 3, wherein the metal tape is attached to a surface opposite to a contact surface with which the contact portion of the fixing member contacts.   The fixing device according to claim 1, wherein the fixing member includes a plurality of layers stacked in a thickness direction, and an intermediate layer of the fixing member is a metal layer as the magnetic body.   The fixing device according to claim 1, wherein the separation member is disposed above the fixing member.   8. The fixing device according to claim 1, further comprising an auxiliary spring that biases the separation member in a direction in which the separation member approaches the fixing member. 9.   An image forming apparatus comprising the fixing device according to claim 1.

Images