Abstract: A fixing device is provided with a heating member, a pressing member, a coil, a fixed core, a movable core and a shielding member provided on the movable core and a position switching unit moving the shielding member between a shielding position where a ring part shields magnetism and a retracted position where the ring part does not shield magnetism. A first area requiring magnetic shielding and a second area not requiring magnetic shielding are selectively set in the heating member. The shielding member includes a first annular portion provided at a position corresponding to a boundary part between the first and second areas, and the first annular portion has a shape closed in a circumferential direction and is electrically insulated at a circumferential part when viewed in an axial direction of the movable core.

Abstract: A fixing unit for fixing a toner image onto paper has a member to be heated and a pressurizing member configured to press against the member to be heated and fix the toner image to the paper. At least one coil surface is disposed along one surface of the member to be heated and includes a coil to generate a magnetic field for inductively heating the member. A magnetism shielding member is disposed near the coil surface. A switch includes a first member to allow passage of the magnetic field and a second member to prevent passage of the magnetic field. The amount of heat for the member when the switch is in a first position where the second member is close to the magnetism shielding member is smaller than when the switch is in a second position where the second member is distanced from the magnetism shielding member.

Abstract: A fixing device includes a heating member, a pressing member, a coil, a magnetic core, a path switching member switching a magnetic path between a first path and a second path, and a magnetism adjustment member. The magnetism adjustment member allows a passage of a magnetic flux from the magnetic core towards the heating member within the magnetic field range when the magnetic field path is switched to the first path, and shields the magnetic flux without allowing the passage of the magnetic flux within the magnetic field range when the magnetic path is switched to the second path. Further, the magnetism adjustment member has a plurality of ring-shaped portions formed of a single wire material having an endless shape. Each of the ring-shaped portions extends in a longitudinal direction of the magnetic core according to a size of the sheet.

Abstract: A fixing device includes an induction coil, a heating rotary belt including a heat generating layer thinner than a magnetic-field penetration depth, a pressure receiving member, a pressing rotator, a magnetic core section, and a movable guiding section. The movable guiding section is a substantially cylindrical frame body being in contact with the inner surface of the heating rotary belt, includes one or more blocking sections, and is rotatable so as to be able to be positioned in a first blocking position and a first non-blocking position.

Abstract: An image forming apparatus has an image forming station and a fixing unit. The fixing unit includes a coil for generating a magnetic field for induction heating the heating member. A first core made of a magnetic material is arranged fixedly around the coil. A second core made of a magnetic material is between the first core and the heating member in a generation direction of the magnetic field to form a magnetic path in cooperation with the first core and capable of changing a posture thereof. A shield made of a nonmagnetic metal is arranged along the outer surface of the second core to shield magnetism in the magnetic field and a magnetic shielding portion for changing the posture of the second core between a first posture where the shield shields the magnetism and a second posture where the shield does not shield the magnetism.

Abstract: A fixing device includes a rotating fixing body fixes a toner image on a recording medium by heating, the rotating fixing body having a cylindrical metal core formed of a magnetic shunt alloy and having a thickness less than a magnetic-field permeation depth at a temperature higher than or equal to a Curie temperature of the metal core, a coil provided along an outer surface of the rotating fixing body so as to generate magnetic flux that subjects the rotating fixing body to induction heating, and an electrically conductive arch-shaped saddle ring member disposed at a position opposing the coil with the metal core being disposed therebetween and in an orientation such that magnetic flux leakage associated with loss of ferromagnetism of the metal core penetrates the ring member.

Abstract: An image forming apparatus includes a fixing unit fixing a toner image onto a sheet. The fixing unit includes a heating member having a sheet conveyed region that is set in accordance with the size of the sheet. The fixing unit further includes a coil generating magnetic field, a fixed core forming a magnetic path, movable cores forming a magnetic path together with the fixed core and arranged along the sheet conveyed region, a shielding member arranged on at least one movable core and shielding magnetism, and a magnetism adjustment unit rotating at least one movable core to switch the position of the shielding member between a shielding position where the shielding member is positioned inside the sheet conveyed region to shield the magnetism and a retracted position where the shielding member is positioned outside the sheet conveyed region to permit pass of the magnetism.

Abstract: An image forming apparatus includes an image forming unit and a fixing unit. The fixing unit includes a heating member; a coil arranged along an outer surface of the heating member for generating a magnetic field for induction heating the heating member; a core arranged to face the heating member with the coil located therebetween in order to form a magnetic path around the coil and made of a magnetic material; a shielding member arranged near the magnetic path generated by the coil, including a closed frame portion and made of a nonmagnetic metal; and a magnetic shielding portion for displacing the shielding member between a retracted position for permitting a magnetic flux to pass along a frame surface virtually formed inside the closed frame portion and a shielding position for shielding magnetism by the penetration of a magnetic flux inside the frame surface.

Abstract: A fixing unit (14) of an image forming apparatus (1) includes a heating member (48) having a first area where a sheet does not come into contact with the heating member (48) and a second area where the sheet comes into contact with the heating member (48). The fixing unit (14) further includes a coil (52) forming a magnetic field, cores (54,56) forming a magnetic path near the coil (52), a nonmagnetic magnetism adjusting member (90) arranged on the magnetic path and having a closed frame, and a switcher (58,60) capable of switching the magnetism adjusting member (90) between a first state where the magnetism adjusting member (90) generates an induction current resulting from the magnetic field to shield the magnetism in the first area, and a second state where the magnetism adjusting member (90) generates no induction current and the magnetism is not shielded in the first area.

Abstract: A fixing device is provided with a heating member, a pressing member, a coil, a fixed core, a movable core and a shielding member provided on the movable core and a position switching unit moving the shielding member between a shielding position where a ring part shields magnetism and a retracted position where the ring part does not shield magnetism. A first area requiring magnetic shielding and a second area not requiring magnetic shielding are selectively set in the heating member. The shielding member includes a first annular portion provided at a position corresponding to a boundary part between the first and second areas, and the first annular portion has a shape closed in a circumferential direction and is electrically insulated at a circumferential part when viewed in an axial direction of the movable core.

Abstract: A fixing device includes a heating member, a pressing member, a coil, a magnetic core, a path switching member switching a magnetic path between a first path and a second path, and a magnetism adjustment member. The magnetism adjustment member allows a passage of a magnetic flux from the magnetic core towards the heating member within the magnetic field range when the magnetic field path is switched to the first path, and shields the magnetic flux without allowing the passage of the magnetic flux within the magnetic field range when the magnetic path is switched to the second path. Further, the magnetism adjustment member has a plurality of ring-shaped portions formed of a single wire material having an endless shape. Each of the ring-shaped portions extends in a longitudinal direction of the magnetic core according to a size of the sheet.

Abstract: A fixing device of an image forming apparatus includes a magnetic core forming a magnetic path composed of a first path for induction-heating a specified area of a heating member and a second path for induction-heating only a smaller area as a reduction of the specified area and the magnetic field being composed of a common magnetic field region where both the first and the second paths pass and an uncommon magnetic field region where only the first path passes; and a magnetism adjusting member arranged at least over the uncommon magnetic field region and permitting the passage of magnetic fluxes propagating toward the heating member from the magnetic core in the uncommon magnetic field region when the magnetic path is switched to the first path while suppressing the passage of the magnetic fluxes in the uncommon magnetic field region when the magnetic path is switched to the second path.

Abstract: A fixing device has a heating roller with a heat source therein. A power supply operates the heat source for heating a transfer material and fixing a toner image thereon. A pressure roller is spaced from the heating roller and a facing member faces the heating roller. An endless fixing belt is mounted on the facing member and the heating roller and contacts the pressure roller to form a nip. A temperature detector faces the outer surface of the fixing belt for detecting the surface temperature thereof. An excessive temperature preventer faces part of the outer surface of the heating roller where the fixing belt is not mounted for detecting the surface temperature of the heating roller and cutting off the power supply to the heat source when the surface temperature rises above a preset temperature.

Abstract: A fixing unit for fixing a toner image onto paper has a member to be heated and a pressurizing member configured to press against the member to be heated and fix the toner image to the paper. At least one coil surface is disposed along one surface of the member to be heated and includes a coil to generate a magnetic field for inductively heating the member. A magnetism shielding member is disposed near the coil surface. A switch includes a first member to allow passage of the magnetic field and a second member to prevent passage of the magnetic field. The amount of heat for the member when the switch is in a first position where the second member is close to the magnetism shielding member is smaller than when the switch is in a second position where the second member is distanced from the magnetism shielding member.

Abstract: A fixing unit of an image forming apparatus includes a coil arranged along an outer surface of the heating member and generating a magnetic field, a first core arranged opposite the heating member with respect to the coil and forming a magnetic path, a second core so fixed between the first core and the heating member with respect to a direction in which the coil generates the magnetic field, as to form the magnetic path together with the first core, a shielding member positioned outward of the second core and shielding the magnetism in the magnetic path, and a magnetism adjusting unit moving the shielding member outward of the second core to switch the position of the shielding member between a shielding position where the shielding member shields the pass of the magnetism and a retracted position where the shielding member permits the pass of the magnetism.

Abstract: An image forming apparatus includes an image forming unit and a fixing unit. The fixing unit includes a heating member; a coil arranged along an outer surface of the heating member for generating a magnetic field for induction heating the heating member; a core arranged to face the heating member with the coil located therebetween in order to form a magnetic path around the coil and made of a magnetic material; a shielding member arranged near the magnetic path generated by the coil, including a closed frame portion and made of a nonmagnetic metal; and a magnetic shielding portion for displacing the shielding member between a retracted position for permitting a magnetic flux to pass along a frame surface virtually formed inside the closed frame portion and a shielding position for shielding magnetism by the penetration of a magnetic flux inside the frame surface.

Abstract: An image forming apparatus includes a fixing unit fixing a toner image onto a sheet. The fixing unit includes a heating member having a sheet conveyed region that is set in accordance with the size of the sheet. The fixing unit further includes a coil generating magnetic field, a fixed core forming a magnetic path, movable cores forming a magnetic path together with the fixed core and arranged along the sheet conveyed region, a shielding member arranged on at least one movable core and shielding magnetism, and a magnetism adjustment unit rotating at least one movable core to switch the position of the shielding member between a shielding position where the shielding member is positioned inside the sheet conveyed region to shield the magnetism and a retracted position where the shielding member is positioned outside the sheet conveyed region to permit pass of the magnetism.

Abstract: An image forming apparatus is provided with an image forming station and a fixing unit including a heating member. The fixing unit includes a coil for generating a magnetic field for induction heating the heating member; a first core arranged to face the heating member with the coil located therebetween; a bar-shaped second core including a cut-off portion and arranged in a magnetic path between the first core and the heating member, when seen in a magnetic field generation direction by the coil, to form the magnetic path together with the first core; and a magnetic adjusting mechanism for changing the posture of the second core between a first posture for guiding a magnetic field by retracting the cut-off portion from the magnetic path and a second posture for increasing magnetic resistance by locating the cut-off portion in the magnetic path by rotating the second core about an axis thereof.

Abstract: A fixing device (30) has a fixing member (30) adapted to be heated by induction heating based on a magnetic field from an induction coil (34). A pressing member (40) is disposed in contact with the fixing member (30) to define therebetween a nip zone (N) for passing a sheet (P) therethrough. The fixing member includes a heating layer (32). The heating layer (32) has a temperature-sensitive metal layer (321) formed on the side of the induction coil (34), and a nonmagnetic-metal layer (322) laminated onto the temperature-sensitive metal layer (321). The nonmagnetic metal layer (321) is made of a metal (copper (Cu)) having a specific resistance less than that of aluminum, and formed to have a thickness (30 ?m) allowing the nonmagnetic metal layer to be substantially free from a temperature rise due to the induction heating.

Abstract: An image forming apparatus has an image forming station and a fixing unit. The fixing unit includes a coil for generating a magnetic field for induction heating the heating member. A first core made of a magnetic material is arranged fixedly around the coil. A second core made of a magnetic material is between the first core and the heating member in a generation direction of the magnetic field to form a magnetic path in cooperation with the first core and capable of changing a posture thereof. A shield made of a nonmagnetic metal is arranged along the outer surface of the second core to shield magnetism in the magnetic field and a magnetic shielding portion for changing the posture of the second core between a first posture where the shield shields the magnetism and a second posture where the shield does not shield the magnetism.