JP5183233B2 - Fixing unit and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a fixing unit that fixes a toner image transferred onto a recording medium onto the recording medium, and an image forming apparatus including the fixing unit.

  Conventionally, as a fixing unit for fixing a toner image transferred onto a recording medium onto the recording medium, one disclosed in Patent Document 1 is known. The fixing unit of Patent Literature 1 heats a toner image on a recording medium and fixes the toner image on the recording medium, and a heating roller (heat generation layer) disposed inside the heating roller and generates heat by the magnetic flux. And a cylindrical heat insulating material (heat insulating layer) disposed between the heating roller and the induction coil.

The heat insulating layer is provided in order to prevent radiant heat (so-called radiant heat) from the heat generating layer from heating the induction coil and burning the induction coil.
JP 2000-105516 A

  In recent years, it has been required to shorten the warm-up time of the fixing unit, that is, to shorten the time required for the heating roller to generate heat up to a predetermined temperature. However, if the heat insulating layer is disposed between the heat generating layer and the induction coil, the distance between the heat generating layer and the induction coil becomes large, which decreases the magnetic coupling between the heat generating layer and the induction coil, and generates heat. The heat generation efficiency of the layer becomes worse. As a result, it is difficult to meet the above requirements.

  In view of the above problems, the present invention provides a fixing unit capable of improving the heat generation efficiency of the heat generating layer and shortening the warm-up time of the fixing unit, and an image forming apparatus including the same. For the purpose.

In order to achieve the above object, a fixing unit according to the present invention fixes a toner image transferred onto a recording medium onto the recording medium, and heats the toner image on the recording medium. A heating rotator for fixing the toner image on the recording medium is provided. The heating rotator is provided in a cylindrical and hollow rotator base, a magnetic flux generator provided inside the rotator base, and generates a magnetic flux, and is provided on the rotator base. A heat generating layer that generates heat and heats the toner image, and a heat insulating property that is provided between the rotating body base and the heat generating layer to prevent heat of the heat generating layer from being transmitted to the magnetic flux generation unit. And a magnetic member that is disposed between the rotating body base and the magnetic flux generation part and guides the magnetic flux from the magnetic flux generation part to the heat generation layer. The magnetic flux generator includes a cylindrical bobbin extending in the longitudinal direction of the rotating body base, a magnetic core disposed inside the bobbin, and a coil wound around the bobbin. Furthermore, the magnetic member is disposed on the inner peripheral surface of the rotating body base, and is disposed on the outer peripheral surface of the first magnetic member having a shape extending from the inner peripheral surface toward the magnetic flux generating portion. And a second magnetic member having a shape extending from the outer peripheral surface toward the rotating body base so as to face the first magnetic member in the radial direction or the longitudinal direction of the rotating body base.

  According to the fixing unit of the present invention, the magnetic flux is guided from the magnetic flux generator to the heat generating layer via the magnetic member disposed between the rotating body base and the magnetic flux generator, in other words, the magnetic flux generator and the heat generator. Since a magnetic path via a magnetic member can be formed between the layers, even if a heat insulating layer is interposed between the magnetic flux generation portion and the heat generation layer, the degree of magnetic coupling between the magnetic flux generation portion and the heat generation layer can be increased. As a result, it is possible to improve the heat generation efficiency of the heat generating layer and to shorten the warm-up time of the heating rotator.

In another preferred embodiment of the present invention, the first magnetic member and the second magnetic member are close to each other via a gap in the radial direction or the longitudinal direction, and the gap is 0.5 mm to 4 mm. It is set in the range of 0 mm.

  The magnetic member is arranged on both the inner peripheral surface of the rotating body base and the outer peripheral surface of the bobbin, and the gap between the magnetic members is set in the range of 0.5 mm to 4.0 mm, for example, so that the heat generating layer and the magnetic flux The degree of magnetic coupling between the generating portions can be further increased as compared with a configuration in which the magnetic member is disposed only on one of the inner peripheral surface of the rotating body base and the outer peripheral surface of the bobbin.

  In still another preferred embodiment of the present invention, a plurality of the magnetic cores of the bobbin are arranged inside the bobbin so as to be movable in the longitudinal direction of the rotating body substrate. According to this configuration, it is possible to adjust the magnetic flux distribution range along the longitudinal direction by moving the plurality of magnetic cores in the longitudinal direction of the rotating base material. Therefore, the heat generation range in the heat generation layer can be adjusted along the longitudinal direction. Accordingly, when the recording medium is, for example, a sheet, the toner image on the sheet can be heated and fixed on the sheet according to the size of the sheet.

  In still another preferred embodiment of the present invention, the fixing unit further includes a blower disposed so as to allow the air to flow inside the rotating body base so as to cool the magnetic flux generation unit. The magnetic member and the second magnetic member have a predetermined angle with respect to the axis of the rotating body base so that the wind forms a spiral airflow that flows from one end of the rotating base to the other end. And arranged on the inner peripheral surface of the rotating body base and the outer peripheral surface of the bobbin.

  According to this configuration, the first magnetic member and the second magnetic member are arranged on the inner peripheral surface of the rotating body base and the outer peripheral surface of the bobbin at a predetermined angle with respect to the axis of the rotating base. As a result, the first magnetic member and the second magnetic member can smoothly flow the wind inside the rotating body base material without blocking the wind from the blower, so that the magnetic flux generator can be efficiently cooled. It is.

  In still another preferred embodiment of the present invention, an image forming apparatus is provided that includes a transfer unit that transfers a toner image formed on a photosensitive drum to a recording medium, and a fixing unit having the above-described configuration.

  According to the fixing unit and the image forming apparatus including the fixing unit according to the present invention, it is possible to improve the heat generation efficiency of the heat generating layer and to shorten the warm-up time of the fixing unit.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a schematic diagram of an image forming apparatus including a fixing unit according to an embodiment of the present invention. The image forming apparatus 10 is, for example, a printer, and includes a sheet storage unit 12 that stores sheets M (recording medium) to be used for printing processing, and one sheet fed out from the sheet bundle M1 stored in the sheet storage unit 12. A transfer unit 13 for performing an image transfer process on the paper M and a fixing unit 20 for performing a fixing process on the paper M subjected to the transfer process by the transfer unit 13 are incorporated in the apparatus main body 11. The paper discharge unit 15 for discharging the paper M on which the fixing process has been performed by the fixing unit 20 is provided at the top of the apparatus main body 11.

  A predetermined number (one in the embodiment) of paper cassettes 121 is provided in the paper storage unit 12 so as to be detachable from the apparatus main body 11. At the downstream end of the paper cassette 121 (on the right side in FIG. 1), a pickup roller 122 that feeds the paper M one by one from the paper bundle M1 is provided. The sheet M fed from the sheet cassette 121 by driving the pickup roller 122 is fed to the transfer unit 13 via the sheet feeding conveyance path 123 and the registration roller pair 124 provided at the downstream end of the sheet feeding conveyance path 123. It has come to be.

  The transfer unit 13 performs a transfer process on the paper M based on image information transmitted from a computer or the like, and is provided to be rotatable around a drum axis extending in the front-rear direction (a direction perpendicular to the paper surface of FIG. 1). A charger 132, an exposure device 133, a developing device 134, a transfer roller 135, and a cleaning device 136 are arranged from the position immediately above the photosensitive drum 131 in the clockwise direction along the peripheral surface of the photosensitive drum 131. It is formed by.

  The photosensitive drum 131 is for forming an electrostatic latent image and a toner image along the electrostatic latent image on the peripheral surface, and an amorphous silicon layer is laminated on the peripheral surface, thereby forming these images. It is suitable for making it happen.

  The charger 132 forms a uniform charge on the circumferential surface of the photosensitive drum 131 rotating clockwise around the drum axis. In the example shown in FIG. A method of applying a charge to the peripheral surface is adopted. A charging roller that applies a charge while rotating the driven surface while contacting the peripheral surface of the photosensitive drum 131 is used instead of the charger 132 as a member that applies a charge to the peripheral surface of the photosensitive drum 131. Also good.

  The exposure device 133 irradiates the peripheral surface of the rotating photosensitive drum 131 with a laser beam to which intensity is applied based on image information transmitted from an external device such as a computer, and the photosensitive drum 131 is rotated by this. An electrostatic latent image is formed on the peripheral surface of the photosensitive drum 131 by erasing the charge of the portion irradiated with the laser beam on the surface.

  The developing device 134 supplies the toner to the peripheral surface of the photosensitive drum 131 to attach the toner to the portion where the electrostatic latent image is formed on the peripheral surface, whereby the toner image is formed on the peripheral surface of the photosensitive drum 131. It is to be formed.

  The transfer roller 135 transfers a positively charged toner image formed on the peripheral surface of the photosensitive drum 131 to the paper M with respect to the paper M sent to a position immediately below the photosensitive drum 131. A negative charge having a polarity opposite to that of the image is applied to the paper M.

  The sheet M that has reached the position directly below the photosensitive drum 131 is pressed and sandwiched between the transfer roller 135 and the photosensitive drum 131, while the positively charged toner image on the circumferential surface of the photosensitive drum 131 is negatively charged. The paper M is peeled off toward the front surface, whereby the paper M is transferred.

  The cleaning device 136 is for removing the toner remaining on the peripheral surface of the photosensitive drum 131 after the transfer process and cleaning it. The peripheral surface of the photosensitive drum 131 cleaned by the cleaning device 136 goes to the charger 132 again for the next image forming process.

  The fixing unit 20 performs a fixing process by heating the toner image on the paper M that has been transferred by the transfer unit 13. The fixing unit 20 heats the toner image on the paper M to fix the toner image on the paper M. It has a cylindrical heating roller (heating rotator) 30 and a cylindrical pressure roller 40 that is disposed below the heating roller 30 so as to sandwich the sheet M between the heating roller 30. The heating roller 30 and the pressure roller 40 are disposed in the box body 21. A rotational driving force is applied to the heating roller 30 from an unillustrated driving device and a speed reduction mechanism disposed in the box body 21. As the heating roller 30 is driven to rotate, the pressure roller 40 is driven and rotated. A nip N is formed between the heating roller 30 and the pressure roller 40. The paper M transferred by the transfer unit 13 is fed toward the nip N between the heating roller 30 and the pressure roller 40. By passing through the nip portion N, the sheet M obtains heat from the heating roller 30 and is subjected to a fixing process. The sheet M subjected to the fixing process is discharged to the paper discharge unit 15 through the paper discharge conveyance path 143.

  The paper discharge unit 15 is formed by recessing the top of the apparatus main body 11, and a paper discharge tray 151 for receiving the discharged paper M is formed at the bottom of the concave recess.

  Hereinafter, the configuration of the fixing unit 20 according to the present embodiment will be described. FIG. 2 is a perspective view showing a state in which the heating roller 30 and the pressure roller 40 are arranged in the box body 21. The heating roller 30 and the pressure roller 40 have axes C1 and C2, respectively. The box 21 has a shape extending in the direction of the axis C1 of the heating roller 30 and the axis C2 of the pressure roller 40, that is, the longitudinal direction of the heating roller 30 and the pressure roller 40. In this box 21, the heating roller 30 and the pressure roller 40 are arranged in a state of being opposed to each other in the vertical direction and in contact with each other along the axial centers C1 and C2. The sheet M transferred by the transfer unit 14 is guided to a nip N (FIG. 1) between the heating roller 30 and the pressure roller 40 through an opening (not shown) formed in the box 21.

  FIG. 3 is a cross-sectional view taken along the line AA in FIG. 2 and shows the constituent layers of the heating roller 30 and the pressure roller 40. The heating roller 30 is a cylindrical member having a substantially circular cross section, a heating belt portion 32 that heats the paper M on which the toner image is formed during the fixing process, a concentricity with the heating belt portion 32, and the heating belt. And a magnetic flux generation unit 36 that is disposed inside the unit 32 and generates a magnetic flux to cause the heating belt unit 32 to generate heat by the magnetic flux. An air layer 34 is interposed between the heating belt portion 32 and the magnetic flux generation portion 36. The heating belt portion 32 is configured to be rotatable with respect to the magnetic flux generation portion 36.

  The heating belt portion 32 includes a cylindrical and hollow roller base material (rotary body base material) 35 having an axis C1 as an axis, and heat insulation provided on the outer peripheral surface of the roller base material 35 concentrically with the roller base material 35. And a heat generating layer 31 provided on the outer peripheral surface of the heat insulating layer 33 concentrically with the roller base material 35.

  The roller base 35 is manufactured from a rigid member capable of imparting mechanical strength to the heating roller 30, for example, a ceramic material. This ceramic material is a ceramic material having non-magnetic and non-conductive characteristics. The thickness of the roller base material 35 is set to 1.0 mm, for example.

  The heat generating layer 31 is formed of an alloy containing nickel and having a thickness of about 40 μm, an elastic layer having elasticity provided on the outer peripheral surface of the heat generating layer base, and an outer peripheral surface of the elastic layer. And a release layer that forms the outermost layer of the heating roller 30. The elastic layer is made of, for example, silicon rubber and has a thickness set to 300 μm. The release layer is obtained, for example, by coating a fluororesin paint (coating agent) such as PFA on the outer peripheral surface of the elastic layer with a thickness in the range of about 10 to 100 μm, for example. This release layer improves the releasability when the toner image is melted and fixed at the nip N between the heating roller 30 and the pressure roller 40.

  The heat insulating layer 33 is made of, for example, silicon sponge having heat insulating properties and elasticity, and heat of the heat generating layer 31 generated by the magnetic flux generating unit 36 to be described later becomes radiant heat (so-called heat) to heat the magnetic flux generating unit 36. In order to prevent the magnetic flux generator 36 from being burned out. The thickness of the heat insulation layer 33 is set to 5.0 mm, for example.

  The magnetic flux generator 36 is configured to be able to heat the heating belt portion 32 by electromagnetic induction, extends concentrically with the axial center C1 of the heating roller 30 and extends in the longitudinal direction of the heating roller 30, and is arranged inside the heating belt portion 32. A cylindrical bobbin 37 made of a liquid crystal polymer, a plurality of magnetic cores 39 having an arcuate cross section centered on an axis C1 disposed in contact with the inner peripheral surface of the bobbin 37, and a bobbin 37 A so-called radial coil (Litz wire) 38 wound around the outer peripheral surface. The magnetic core 39 is, for example, a ferrite core, has a shape extending in the longitudinal direction of the bobbin 37, and is arranged in two rows so as to form an annular core with the two magnetic cores 39 as shown in FIG. Yes.

  When a high frequency current is supplied to the coil 38 from a high frequency power supply (not shown), a magnetic flux is generated from the coil 38. The magnetic flux travels outward in the radial direction of the bobbin 37 and reaches the heat generating layer base material of the heat generating layer 31. Thereby, magnetic paths P, P1, and P2 (FIG. 6) described later are formed, and the heat generating layer base material generates heat. The toner image on the paper M is melted and fixed at the nip portion N by the heat of the heat generating layer base material.

  The pressure roller 40 is arranged concentrically with the axis C2 and is made of a non-magnetic metal roller base (not shown), an elastic layer (not shown) provided on the outer peripheral surface of the roller base, and an outer periphery of the elastic layer. And a release layer (not shown) provided on the surface. Examples of the nonmagnetic metal of the roller base material include aluminum, copper, silver, and austenitic stainless steel. The thickness of the roller base material is set to about 1 to 5 mm, for example, to give mechanical strength to the roller base material. The elastic layer and the release layer of the pressure roller 40 are made of the same material as the elastic layer and the release layer of the heating roller 30.

  A thermistor 43 for detecting the temperature of the outer peripheral surface of the heating roller 30 is disposed at a position spaced a predetermined distance outward in the radial direction of the heating roller 30. The thermistor 43 is a ceramic semiconductor that uses metal oxide as a main raw material and is sintered at a high temperature, and has a negative temperature coefficient that decreases as the temperature rises. That is, the temperature of the heat generating layer 31 is detected. A high-frequency current supplied to a coil 38 (to be described later) is adjusted by a control unit (not shown) based on a signal indicating the outer surface temperature of the heating roller 30 detected by the thermistor 43, and the outer surface temperature of the heating roller 30 is predetermined. The temperature is controlled so as to be maintained.

  FIG. 4A is an enlarged cross-sectional view of the heating belt portion 32 of the heating roller 30. A plurality of pairs of left and right first magnetic members 50, 50 in FIG. 4A are attached to the inner peripheral surface of the roller base 35 of the heating belt portion 32 along the longitudinal direction of the roller base 35. The first magnetic member 50 is a member having a cross-sectional arc shape having a shape along the inner peripheral surface of the roller base material 35, and protrudes outward at both end portions in the arc direction as shown in FIG. 4B. An engaging protrusion 51 is provided. On the inner peripheral surface of the roller base material 35, a locking hole 55 that can engage with the engaging protrusion 51 of the first magnetic member 50 is formed. The first magnetic member 50 is fixed to the roller base 35 by applying an adhesive to the outer peripheral surface thereof and engaging the engaging protrusions 51 with the locking holes 55 of the roller base 35. The engaging protrusions 51 of the first magnetic member 50 are in contact with the heat insulating layer 33 so as to be flush with the outer peripheral surface of the roller base 35. The first magnetic member 50 is made of, for example, a ferrite core.

  FIG. 5A is an enlarged cross-sectional view of the magnetic flux generator 36 of the heating roller 30. A plurality of pairs of left and right second magnetic members 53, 53 in FIG. 5A are attached to the outer peripheral surface of the bobbin 37 of the magnetic flux generator 36 along the longitudinal direction of the bobbin 37. The second magnetic member 53 is a member having a circular arc shape having a shape along the outer peripheral surface of the bobbin 37. As shown in FIG. 5B, the engagement protrusion protruding inward at both ends in the arc direction. 54. On the outer peripheral surface of the bobbin 37, a locking hole 57 is formed in which the engaging protrusion 54 of the second magnetic member 53 can be engaged. The second magnetic member 53 is fixed to the bobbin 37 by applying an adhesive to the inner peripheral surface thereof and engaging the engaging protrusions 54 with the locking holes 57 of the bobbin 37. The engagement protrusion 54 of the second magnetic member 53 is in contact with the magnetic core 39 while being flush with the inner peripheral surface of the bobbin 37. The coil 38 that is radially wound around the bobbin 37 is divided by the second magnetic member 53 in the longitudinal direction of the bobbin 37. Similar to the first magnetic member 50, the second magnetic member 53 includes a ferrite core.

  FIG. 6 is a cross-sectional view of the heating roller 30 cut along the longitudinal direction, and shows the positional relationship between the first magnetic member 50 and the second magnetic member 53. The first magnetic member 50 attached to the inner peripheral surface of the roller base 35 and the second magnetic member 53 attached to the outer peripheral surface of the bobbin 37 are opposed to each other in the air layer 34 and the heating roller 30. It arrange | positions so that it may space apart via the clearance gap G in radial direction. By disposing the first magnetic member 50 and the second magnetic member 53 in the heating roller 30 in this way, the magnetic core 39, the second magnetic member 53, the gap G, the first magnetic member 50, the heat insulating layer 33, and the heat generation. A magnetic path P through which the magnetic flux generated by the coil 38 passes is formed between the layers 31.

  Since the heat insulation layer 33 and the air layer 34 are interposed between the magnetic flux generation part 36 and the heat generation layer 31, the distance between the magnetic flux generation part 36 and the heat generation layer 31 is large. However, the magnetic flux generated in the coil 38 can be smoothly guided to the heat generating layer 31 by the magnetic path P via the first magnetic member 50 and the second magnetic member 53. As a result, the degree of magnetic coupling between the magnetic flux generator 36 and the heat generating layer 31 can be increased, so that the heat generation efficiency of the heat generating layer 31 can be improved, and consequently the warm-up time of the heating roller 30 can be shortened. be able to. The gap G between the first magnetic member 50 and the second magnetic member 53 is preferably set in the range of 0.5 mm to 4.0 mm. Within this range, the degree of magnetic coupling between the magnetic flux generator 36 and the heat generating layer 31 does not decrease.

  FIG. 7 is a cross-sectional view taken along the longitudinal direction of the heating roller 30 and shows another arrangement relationship of the first magnetic member 50 and the second magnetic member 53. The first magnetic member 50 and the second magnetic member 53 are disposed in the air layer 34 so as to face the longitudinal direction of the bobbin 37 (that is, the longitudinal direction of the heating roller 30) via the gap G ′. By arranging the first magnetic member 50 and the second magnetic member 53 in the heating roller 30 in this way, the magnetic core 39, the second magnetic member 53, the gap G ′, the first magnetic member 50, the heat insulating layer 33, and A magnetic path P ′ through which the magnetic flux generated by the coil 38 passes is formed between the heat generating layers 31. Also by the magnetic path P ′, the magnetic flux generated by the coil 38 can be smoothly guided to the heat generating layer 31. As a result, the degree of magnetic coupling between the magnetic flux generator 36 and the heat generating layer 31 can be increased, so that the heat generation efficiency of the heat generating layer 31 can be improved, and consequently the warm-up time of the heating roller 30 can be shortened. be able to.

  The gap G ′ between the first magnetic member 50 and the second magnetic member 53 is 0.5 mm to 4.0 mm, similarly to the arrangement relationship between the first magnetic member 50 and the second magnetic member 53 shown in FIG. It is preferable to set the range. Within this range, the degree of magnetic coupling between the magnetic flux generator 36 and the heat generating layer 31 does not decrease.

  Further, when the bobbin 37 and the heating belt portion 32 are swung from the axial center C1 of the heating roller 30 due to the pressing force received from the pressure roller 40 during the fixing process, the first magnetic There is a possibility that the member 50 and the second magnetic member 53 come into contact with each other. However, since the first magnetic member 50 and the second magnetic member 53 are arranged so as to be shifted in the longitudinal direction of the heating roller 30 via the gap G ′, the first magnetic member 50 and the heating belt portion 32 are swung. The contact between the member 50 and the second magnetic member 53 can be avoided.

  As shown in FIG. 6, the plurality of magnetic cores 39 arranged on the inner peripheral surface of the bobbin 37 have a shape extending along the coil 38 that is radially wound around the bobbin 37 and parallel to the heat generating layer 31. Have. Among the plurality of magnetic cores 39, the magnetic cores 39 disposed at both ends in the longitudinal direction of the bobbin 37 are disposed so as to be movable in the longitudinal direction along the inner peripheral surface of the bobbin 37. The magnetic core 39 before movement is indicated by a solid line, and the magnetic core 39 after movement is indicated by an imaginary line. In addition, the magnetic core 39 before moving forms a magnetic path P <b> 1 between the second magnetic member 53, the gap G, the first magnetic member 50, the roller base 35, the heat insulating layer 33, and the heat generating layer 31. When the magnetic core 39 is moved in the longitudinal direction, the magnetic path P1 is moved in the longitudinal direction to form the magnetic path P2. In other words, the distribution range of the magnetic flux generated by the coil 38 can be adjusted along the longitudinal direction of the heating roller 30. Therefore, the heat generation range in the heat generating layer 31 of the heating belt portion 32 can be adjusted along the longitudinal direction of the heating roller 30. Accordingly, the toner image on the paper M can be heated and fixed on the paper M according to the sizes W1 and W2 of the paper M.

  In FIG. 6, the magnetic path P <b> 1 is formed by moving the magnetic core 39 according to the size W <b> 1 of the paper M, while the magnetic path P <b> 2 moves the magnetic core 39 according to the size W <b> 2 of the paper M. It is formed by moving. The amount of movement of the magnetic core 39 can be accurately adjusted by moving it using a stepping motor. The configuration that allows the magnetic core 39 to move can also be applied to the heating roller 30 shown in FIG.

  As shown in FIGS. 6 and 7, the heating roller 30 is a blower 45 disposed so as to be able to blow the cooling air S from one end side to the other end side of the magnetic flux generation unit 36 in order to cool the magnetic flux generation unit 36. For example, a blower fan is provided. Since the roller base material 35 is made of a ceramic material, the cooling air S from the blower 45 does not reach the heat generation layer 31 through the roller base material 35 and cool the heat generation layer 31, and does not cool the magnetic flux generation unit. Only the coil 38 of the magnetic flux generator 36 is cooled through the air layer 34 between the roller 36 and the roller base 35.

  FIG. 8 is a cross-sectional view taken along the longitudinal direction of the heating roller 30 and shows yet another arrangement relationship between the first magnetic member 50 and the second magnetic member 53. The plurality of first magnetic members 50 arranged in the longitudinal direction of the heating roller 30 are inner peripheral surfaces of the roller base 35 so as to incline at predetermined angles alternately in different directions when viewed from the axis C1 of the heating roller 30. Is arranged. The adjacent first magnetic members 50 that are alternately inclined in different directions as described above have a C-shape in a cross-sectional view in FIG. Further, like the first magnetic member 50, the plurality of second magnetic members 53 arranged in the longitudinal direction of the heating roller 30 bobbin so as to incline at a predetermined angle alternately in different directions when viewed from the axis C1. 37 is disposed on the outer peripheral surface. Adjacent first magnetic members 50 that are alternately inclined in different directions as described above also have a C shape in a cross-sectional view, similarly to the first magnetic member 50. The first magnetic member 50 and the second magnetic member 53 arranged in a C shape are arranged so as to alternate in the longitudinal direction of the heating roller 30. With such an arrangement relationship, the cooling air S from the blower 45 flows spirally along the outer peripheral surface of the bobbin 37 of the magnetic flux generator 36 in the air layer 34 between the heating belt portion 32 and the magnetic flux generator 36. The helical cooling air S flows smoothly into the roller base 35 without being blocked by the first magnetic member 50 and the second magnetic member 53. Thereby, it is possible to cool the magnetic flux generation part 36 efficiently.

  FIG. 9 is a schematic diagram showing a configuration in which the fixing unit 20 is applied to a so-called pressure belt system. In this configuration, an endless belt 62 stretched between a pair of rollers 60 and 61 is arranged in contact with the heating roller 30 instead of the pressure roller 40. The belt 62 is a substantially intermediate portion between the pair of rollers 60 and 61 and is in contact with the heating roller 30, and the nip portion N is formed between the outer peripheral surface of the intermediate portion and the heating roller 30. Thus, even when the fixing unit 20 is applied to the pressure belt system, the heat generation efficiency of the heat generating layer 31 of the heating roller 30 can be improved, and the warm-up time of the heating roller 30 can be shortened. Can be planned.

1 is a schematic diagram of an image forming apparatus including a fixing unit according to an embodiment of the present invention. FIG. 4 is a perspective view showing a state where a heating roller and a pressure roller of the fixing unit are arranged in a box. It is sectional drawing cut | disconnected along the AA line of FIG. (A) is an expanded sectional view of the heating belt part of a heating roller, (B) is sectional drawing of the 1st magnetic member fixed to a heating belt part. (A) is an expanded sectional view of the magnetic flux generation part of a heating roller, (B) is sectional drawing of the 2nd magnetic member fixed to a magnetic flux generation part. It is sectional drawing of the heating roller which shows the arrangement | positioning relationship of a 1st magnetic member and a 2nd magnetic member. It is sectional drawing of the heating roller which shows the other arrangement | positioning relationship of a 1st magnetic member and a 2nd magnetic member. It is sectional drawing of the heating roller which shows other arrangement | positioning relationship of a 1st magnetic member and a 2nd magnetic member. FIG. 3 is a schematic diagram illustrating a configuration in which a fixing unit is applied to a pressure belt system.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 20 Fixing unit 30,30 'Heating roller 31 Heat generating layer 32 Heating belt part 33 Heat insulating layer 34 Air layer 35 Roller base material 36 Magnetic flux generating part 37 Bobbin 38 Coil 39 Magnetic core 40 Pressure roller 50 1st magnetic member 51 Locking Protrusion 53 Second Magnetic Member 54 Locking Protrusion 55, 57 Locking Hole 60 Fixing Roller 62 Heating Belt P, P1, P2 Magnetic Path S Cooling Air

Claims (5)

A fixing unit for fixing a toner image transferred onto a recording medium onto the recording medium,
A heating rotator for heating the toner image on the recording medium and fixing the toner image on the recording medium;
The heating rotator is
A cylindrical and hollow rotating body substrate;
A magnetic flux generator provided inside the rotating body base material for generating magnetic flux;
A heat generating layer provided on the rotating body substrate and generating heat by the magnetic flux to heat the toner image;
A heat insulating layer provided between the rotating body base and the heat generating layer and having a heat insulating property to prevent heat of the heat generating layer from being transmitted to the magnetic flux generation unit;
A magnetic member disposed between the rotating body base and the magnetic flux generation part to guide the magnetic flux from the magnetic flux generation part to the heat generation layer;
Including
The magnetic flux generation unit includes a cylindrical bobbin extending in a longitudinal direction of the rotating body base, a magnetic core disposed inside the bobbin, and a coil wound around the bobbin,
The magnetic member, the disposed on the inner peripheral surface of the rotary body substrate, a first magnetic member having a shape extending from the inner circumferential surface to the magnetic flux generating section is disposed on the outer peripheral surface of the bobbin, the A fixing unit including a second magnetic member having a shape extending from the outer peripheral surface toward the rotating body base so as to face the first magnetic member in a radial direction or a longitudinal direction of the rotating body base. 2. The fixing unit according to claim 1, wherein the first magnetic member and the second magnetic member are close to each other via a gap in the radial direction or the longitudinal direction, and the gap is 0.5 mm to 4 mm. Fixing unit set in the range of 0mm.   3. The fixing unit according to claim 1, wherein a plurality of the magnetic cores of the bobbin are arranged inside the bobbin so as to be movable in a longitudinal direction of the rotating body base material. The fixing unit according to any one of claims 1 to 3, further comprising a blower disposed so as to cool the magnetic flux generation unit by flowing air inside the rotating body base material.
The first magnetic member and the second magnetic member are arranged with respect to an axial center of the rotating body base so that the wind is a spiral air flow that flows from one end of the rotating base to the other end. A fixing unit disposed on an inner peripheral surface of the rotating body base and an outer peripheral surface of the bobbin at a predetermined angle. A transfer unit for transferring a toner image formed on the photosensitive drum to a recording medium;
The fixing unit according to any one of claims 1 to 4, wherein the toner image is fixed to the recording medium.
An image forming apparatus.

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