JP2012145911A - Fixing device and image forming apparatus including fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of reducing the number of replacement members, and an image forming apparatus.SOLUTION: A fixing device according to an embodiment is provided with: an endless fixing belt having a heating layer with a metal included therein; and a drive transmission part having a magnet that is arranged on one end in the axial direction of the fixing belt, and is connected with the fixing belt by magnetic force.

Description

  Embodiments described herein relate generally to a fixing device and an image forming apparatus including the fixing device.

  As a conventional fixing device, there is a device heated by an electromagnetic induction heating method.

  In the fixing device having this structure, if the fixing device is in contact with the pressure member, the pressure member may be deprived of heat when the temperature of the heating device is increased. In order to prevent this, there is a fixing device that heats only the fixing belt.

JP 2008-176285 A

  However, since the fixing belt and the driving gear are bonded, when the fixing belt is replaced, the driving gear must be replaced at the same time.

  The problem to be solved by the present invention is to provide a fixing device and an image forming apparatus that can reduce the cost of replacement members.

  In order to solve the above-described problems, an exemplary embodiment of a fixing device includes an endless fixing belt including a heat generating layer containing metal, a fixing belt disposed at one end in the axial direction of the fixing belt, and a magnet. And a drive transmission unit connected magnetically.

1 is a schematic configuration diagram showing an MFP equipped with a fixing unit of the present embodiment. FIG. 2 is a schematic configuration diagram of a fixing unit of the present embodiment. The figure which shows the cross section which follows the X-X 'line | wire of FIG. FIG. 3 is an explanatory diagram of a layer configuration of a fixing belt according to the present embodiment. FIG. 4 is a diagram illustrating an inner pole of the fixing belt according to the embodiment. The figure explaining fitting of the fixing belt of this embodiment, and a drive gear.

  FIG. 1 is a schematic configuration diagram illustrating a color MFP (Multi Functional Peripheral) 1 that is an image forming apparatus. The MFP 1 includes a paper feeding unit 5, a printer unit 10 that is an image forming unit, a fixing unit 30, a scanner unit 40, and the like.

  The sheet feeding unit 5 includes a cassette 6 that stores sheets P stacked in a stacked manner, and a pickup roller 7 that feeds the uppermost sheet of the sheets P stored in the cassette 6 to the printer unit 10.

  The printer unit 10 includes four sets of image forming stations 12Y, 12M, 12C, and 12K of Y (yellow), M (magenta), C (cyan), and K (black), and image forming stations 12Y, 12M, 12C, An intermediate transfer belt 20 for transferring a toner image formed by 12K, a laser exposure device 22 for irradiating each image forming station 12Y, 12M, 12C, and 12K with a laser, and the like are provided.

  Each of the image forming stations 12Y, 12M, 12C, and 12K includes photosensitive drums 13Y, 13M, 13C, and 13K. The image forming stations 12Y, 12M, 12C, and 12K have chargers 14Y, 14M that uniformly charge the surfaces of the photosensitive drums 13Y, 13M, 13C, and 13K around the photosensitive drums 13Y, 13M, 13C, and 13K. , 14C and 14K, developing devices 15Y, 15M, 15C and 15K that visualize the electrostatic latent images created on the photosensitive drums 13Y, 13M, 13C, and 13K with toner, and intermediately transfer the visualized toner images The primary transfer rollers 16Y, 16M, 16C, and 16K that transfer to the belt 20 and the photosensitive member that cleans the toner remaining on the photosensitive drums 13Y, 13M, 13C, and 13K without being transferred to the intermediate transfer belt 20 by the primary transfer roller. Body cleaners 17Y, 17M, 17C and 17K are provided. The photosensitive drums 13Y, 13M, 13C, and 13K rotate in the direction of arrow a in FIG.

  The laser exposure device 22 irradiates the photosensitive drums 13Y, 13M, 13C, and 13K with laser beams 22Y, 22M, 22C, and 22K corresponding to the respective colors.

  The printer unit 10 includes a driving roller 20a and a driven roller 20b that support the intermediate transfer belt 15 inside the intermediate transfer belt 20, and travels in the direction of arrow b. The printer unit 10 includes a secondary transfer roller 20c at a position facing the driving roller 20a via the intermediate transfer belt 15.

  A fixing unit 30 for fixing the toner image transferred to the sheet P by the secondary transfer roller is provided above the printer unit 10. The fixing unit 30 will be described in detail with reference to FIG.

  In addition, the MFP 1 includes a paper discharge roller 33 that discharges the sheet P fixed above the fixing unit 30 to the outside of the MFP 1. Further, a sheet P fed from the cassette 6 is guided between the driving roller 20a and the secondary transfer roller 20c to the fixing unit 30 and further guided through the conveying path 36 and the like from the fixing unit 30 to the paper discharge roller 33. Have.

The sheet (recording medium) fed from the cassette 6 by these configurations is transferred with an image formed by the printer unit 10, fixed, and discharged.

Next, the fixing unit 30 will be described in detail. As shown in FIG. 2, the fixing unit 30 includes a fixing belt 50, a press roller 60, an induction current generating coil (hereinafter abbreviated as IH coil) 70, a motor 80 that rotates the fixing belt, and a drive that transmits the power of the motor 80. The transmission gear group 81, the drive gear 90 that receives the power of the drive transmission gear group 81, and the like are provided.
The fixing belt 50 is an endless belt that is hollow inside, and the hollow portion includes a stay 51 and a pad 52 inside. The inner sides of both ends in the axial direction of the endless belt of the fixing belt 50 are hollow. The inside of the fixing belt 50 and one outer peripheral surface of the drive gear 90 are in contact with each other. A driven wheel 95 is provided on the other end side of the fixing belt 50. A sensor 96 that detects the rotation of the driven wheel 95 on the other end side of the fixing belt 50 is disposed.

  FIG. 3 is a view showing a cross section taken along line X-X ′ of FIG. 2. The pad 52 is formed of a heat-resistant silicone sponge or silicone rubber, and has a fluororesin release layer on the surface. The pad 52 is provided on the opposite side of the fixing belt 50 from the side where the press roller 60 is provided, and presses the inner peripheral surface of the fixing belt 50 from the inside.

  The press roller 60 includes an elastic body layer 66 such as a heat-resistant silicone sponge or a silicone rubber layer around a core metal 64, and a release layer 68 made of a fluorine-based resin such as a PFA resin on the surface. .

  The fixing belt 50 has a multilayer structure. As shown in FIG. 4, the fixing belt 50 has a configuration in which layers are formed in order of a heat generation layer 50 a, an elastic layer 50 b, and a release layer 50 c from the inner periphery side to the outer periphery side.

  The heat generating layer 50 a is a layer for generating heat by generating an eddy current by a magnetic field generated from the IH coil 70. Examples of the metal constituting the heat generating layer 50a include Ni, Fe, Cu, Au, Ag, and Al. The metal may be used alone or two or more kinds of alloys may be used. However, Cu, Au, Ag, and Al have low specific resistivity and need to be a thin layer of about 10 μm or less. Therefore, when Cu, Au, Ag, or Al is used, a base material other than Cu, Au, Ag, or Al is further required to maintain the strength of the heat generating layer 50a. As the heat generating layer 50a, for example, a Ni-Cu-Ni three-layer structure can be cited.

  The elastic layer 50b is provided between the heat generating layer 50a and the release layer 50c. The constituent material of the elastic layer 50b is preferably a heat-resistant rubber such as silicone rubber or fluorine.

  FIG. 5 shows the poles of the heat generating layer 50 a inside the fixing belt 50. N poles and S poles are alternately arranged to form an even number of 8 poles in total. Further, the arc length of each pole inside the fixing belt 50 is set to be equal.

  FIG. 6 is an enlarged view of the vicinity of the drive gear 90 of FIG. As shown in FIG. 6, the drive gear 90 includes a gear portion 91, a base portion 92, and a magnet portion 93, and the gear portion 91 and the magnet portion 93 are provided with the base portion 92 at the center. The magnet portion 93 has a columnar shape, and N and S poles are alternately provided on the peripheral surface, so that the total number is 8 even. The lengths of the arcs in the circumferential direction of the poles are set evenly. The diameter of the gear portion 91 is larger than the diameter of the base portion 92, and the diameter of the magnet portion 93 is smaller than the diameter of the base portion 92. The diameter of the magnet portion 93 is almost the same as or slightly smaller than the inner diameter of the fixing belt 50. The side surface portion of the magnet portion and the inside of one end portion of the fixing belt overlap. Since the heat generating layer 50a of the fixing belt 50 is made of metal, the fixing belt 50 and the drive gear 93 are magnetized.

  As a constituent material of the gear portion 91 and the base portion 92 of the drive gear 90, it is preferable to use a resin having high mechanical strength and heat resistance. As the constituent resin material, phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, LCP resin, and the like are suitable. Further, a bearing 91 a is provided in the vicinity of the rotation shaft inside the gear portion 91.

  The inside of one end side where the motor 80 of the fixing belt 50 is disposed is hollow. The magnetized region of the fixing belt 50, that is, the magnet portion 93 is from about 10 mm to 20 mm from one end side in the rotation axis direction of the fixing belt 50. Magnetization of the fixing belt 50 is performed on the heat generating layer 50 a that is the innermost layer of the fixing belt 50.

  The drive gear 90 and the driven wheel 95 are supported by the stay 51 via bearings. The rotation of the driving gear 90 is transmitted to the driven wheel 95 by the rotation of the fixing belt 50.

  A rotation detection sensor 96 is disposed in the vicinity of the driven wheel 95 to detect the rotation of the fixing belt 50. When rotation of the fixing belt 50 is detected by the rotation detection sensor 96, the IH coil 70 starts induction heating. If the rotation of the fixing belt 50 is not detected even though the driving gear 90 is rotating, it can be seen that the driving gear 90 is not reliably magnetized on the fixing belt 50.

  Since the drive gear 90 has the same number of poles as the fixing belt 50, it is surely magnetized. An arrow A in FIG. 6 indicates a direction in which the drive gear 90 is fitted to the fixing belt 50. Due to the magnetic force, the outer peripheral surface of the drive gear 90 is fitted to the inner peripheral surface of the fixing belt 50 in the direction of arrow A. Further, in order to release the fitting between the fixing belt 50 and the drive gear 90a, a force is applied in the direction opposite to the arrow A.

  The number of magnetic poles is preferably 6 or more. If the number of poles is 6 or more, good driving torque can be obtained. The torque does not change so much when the number of poles is 6 or more.

  The magnetic flux density required for the magnetic driving of the fixing belt 50 and the driving gear 90 is found to be obtained when the fixing belt 50 and the driving gear 82a are both 25 mT or more and the driving torque is 30 N · cm or more. Furthermore, the magnitude of the magnetic flux density of the fixing belt 50 and the drive gear 82a is such that the magnetic flux density of the drive gear 82a is larger than that of the fixing belt 60, and 1.0 ≦ Bd / Bb <1.2. It has been found that the minute deformation of the fixing belt 50 can be reduced and the life of the fixing belt 50 can be extended. Bd / Bb is the ratio of the magnetic flux density between the drive gear 90 and the fixing belt 50. If the difference in magnetic flux density is large, a problem that the belt undulates occurs.

  According to the embodiment described above, since the fixing belt 50 and the drive gear 90 are fitted by magnetic force, the labor and cost of the adhesive can be eliminated. Further, since the fitting portion between the fixing belt 50 and the drive gear 90 can be easily separated, it is not necessary to discard the fixing belt 50 and the drive gear 90 at the same time, and the cost of the replacement member can be reduced. Further, it is possible to grasp whether or not the fixing belt 50 is disconnected by the rotation detection sensor 84 provided in the vicinity of the driven wheel 95.

  In this embodiment, the drive transmission gear group is provided only on one end side of the fixing belt 50. However, the drive gear 90 is provided on the other end side, and a shaft is provided in parallel with the rotation axis of the fixing belt 50, and on the other end side. Alternatively, the power of the motor may be transmitted.

  In the present embodiment, since the heat generating layer 50a as the innermost layer of the fixing belt 50 has metal, the drive gear 90 is inserted and magnetized inside the fixing belt 50. However, the present invention is not limited to this. The fixing belt 50 may have a structure in which a magnet is provided on one outer side of the fixing belt 50 and the driving gear is magnetized on the outer side of the fixing belt 50.

  The present invention is not limited to the above embodiments, and various modifications are possible. For example, when a magnetic drive gear is used, only the fixing belt 50 needs to be magnetized. This is because if one side is a magnetic body (for example, iron), even if only one side is a magnet, it is attracted. Alternatively, a fixing belt in which a rubber magnet formed by dispersing phylite powder in rubber is attached to the outer periphery may be used.

  Although an embodiment of the present invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

1 MFP
50 ... Fusing belt 50a ... Heat generation layer 84 ... Rotation detection sensor 90 ... Drive gear 91 ... Gear part 93 ... Magnet part

Claims (6)

An endless fixing belt including a heat generating layer containing metal;
A fixing device that includes a drive transmission unit that is disposed at one end of the fixing belt in the axial direction and includes a magnet and is magnetically connected to the fixing belt.   The fixing device according to claim 1, further comprising an induction current coil disposed on an outer peripheral side of the fixing belt for induction heating the fixing belt. Having a cavity inside the fixing belt and having the heat generating layer in the innermost layer of the fixing belt;
The fixing device according to claim 1, wherein the drive transmission unit is magnetized inside the fixing belt.   If the magnetic flux intensity per unit area of the magnetization of the fixing belt is Bb and the magnetic flux intensity per unit area of the drive transmission unit is Bd, Bb> 25 mT, Bd> 25 mT, and 1.0 ≦ Bd. The fixing device according to claim 1, wherein /Bb<1.2. An image forming unit for forming an image on a recording medium;
An endless fixing belt comprising a heat generating layer containing metal and fixing the image on the recording medium in contact with the recording medium;
A drive transmission unit disposed at one end of the fixing belt in the axial direction and having a magnet and magnetically connecting to the fixing belt;
An image forming apparatus.   The fixing device according to claim 1, further comprising an induction current coil disposed on an outer peripheral side of the fixing belt for induction heating the fixing belt.

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