Image forming apparatus

• US 20060088329A1
• Filed: 10/21/2005
• Published: 04/27/2006
• Est. Priority Date: 10/22/2004
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Nakase, Takahiro, Yoshimura, Yasuhiro, Suzuki, Hitoshi, Yamamoto, Naoyuki, Kondo, Toshiharu
• Granted Patent: US 7,437,113 B2
• Time in Patent Office: Days
• US Class Current: 399/69
• CPC Class Codes: G03G 15/2042 specially for the axial heat partition
• CPC Class Codes: G03G 15/2053 Structural details of heat elements, e.g. structure of roller or belt, eddy current, induction heating
• CPC Class Codes: G03G 2215/2035 the fixing nip having a stationary belt support member opposing a pressure member

Abstract

An image heating apparatus includes a coil for generating a magnetic flux by current flowing therethrough; an image heating member for heating an image on a recording material which is fed therethrough, the image heating member producing heat by eddy current generated by the magnetic flux; electric power supply control means for controlling electric power supply to the coil so as to provide the image heating member with a predetermined temperature; magnetic flux adjusting means for adjusting a magnetic flux in a direction perpendicular to a feeding direction of the recording material, the magnetic flux adjusting means having a first magnetic flux adjusting portion for reducing, by relative movement thereof relative to the coil, a magnetic flux directing toward an end of the image heating member adjacent to a sheet feedable range with respect to the direction, and a second magnetic flux adjusting portion for reducing, by relative movement thereof relative to the coil, a magnetic flux directing toward the image heating member in a sheet feeding range in which at least a minimum size recording material is fed, with respect to the direction; and setting means for setting the relative positions of the first magnetic flux adjusting portion and the second magnetic flux adjusting portion to be taken after continuous feeding of the recording materials having a size smaller than a maximum feedable size of the apparatus.

Claims

1. An image heating apparatus comprising:

a coil for generating a magnetic flux by current flowing therethrough;

an image heating member for heating an image on a recording material which is fed therethrough, said image heating member producing heat by eddy current generated by the magnetic flux;

electric power supply control means for controlling electric power supply to said coil so as to provide said image heating member with a predetermined temperature;

magnetic flux adjusting means for adjusting a magnetic flux in a direction perpendicular to a feeding direction of the recording material, said magnetic flux adjusting means having a first magnetic flux adjusting portion for reducing, by relative movement thereof relative to said coil, a magnetic flux directing toward an end of said image heating member adjacent to a sheet feedable range with respect to the direction, and a second magnetic flux adjusting portion for reducing, by relative movement thereof relative to said coil, a magnetic flux directing toward said image heating member in a sheet feeding range in which at least a minimum size recording material is fed, with respect to the direction; and

setting means for setting said relative positions of said first magnetic flux adjusting portion and said second magnetic flux adjusting portion to be taken after continuous feeding of the recording materials having a size smaller than a maximum feedable size of said apparatus.

2. An apparatus according to claim 1, wherein said first magnetic flux adjusting portion and said second magnetic flux adjusting portion are movable integrally with each other.

3. An apparatus according to claim 1, wherein said magnetic flux adjusting means moves said magnetic flux adjusting portion to a position for reducing the magnetic flux directing toward a high temperature portion of said image heating member.

4. An apparatus according to claim 1, further comprising a first temperature detecting element, disposed in a range where a recording material having a minimum feedable size of said apparatus is fed, for detecting a temperature of said image heating member, and a second temperature detecting element, disposed in a range which is outside the range in which the recording material having the minimum feedable size of said apparatus is fed and which is within the maximum feedable range, for detecting a temperature of said image heating member, wherein said magnetic flux adjusting means are moved in accordance with a difference between the temperatures detected by said first temperature detecting element and said second temperature detecting element.

5. An apparatus according to claim 4, further comprising rotation control means for rotating said image heating member in accordance with the difference between the temperatures detected by said first temperature detecting element and said second temperature detecting element.

6. An apparatus according to claim 1, wherein said first and second magnetic flux adjusting portions are each movable to a first position for decreasing the magnetic flux directing toward said image heating member and a second position for decreasing the magnetic flux to an extent less than at the first position.