Fixing device and image forming apparatus

Patent metadata

Field	Value
Publication number	US-9342002-B2
Application number	US-201314132259-A
Country	US
Kind code	B2
Filing date	Dec 18, 2013
Priority date	Dec 25, 2012
Publication date	May 17, 2016
Grant date	May 17, 2016

Abstract

A fixing device includes a rotary member comprising a heat generation layer; an excitation coil generating magnetic flux, disposed along an axial direction of the rotary member and opposite the rotary member, to heat by induction the heat generation layer; a first demagnetizing coil layered on the excitation coil and generating magnetic flux in a direction reverse to and cancel the magnetic flux that the excitation coil generates; a sheet size detector to obtain a size of a recording sheet on which an image is to be formed by passing through the rotary member; and a drive controller to control driving of the first demagnetizing coil. The drive controller drives the first demagnetizing coil after information including the sheet size information has been obtained.

First claim

What is claimed is:

1. A fixing device comprising:
a rotary member including a heat generation layer;
an excitation coil generating magnetic flux, disposed along an axial direction of the rotary member, to heat by induction the heat generation layer of the rotary member;
a first demagnetizing coil layered on the excitation coil and generating magnetic flux in a direction reverse to and cancelling out the magnetic flux that the excitation coil generates;
a sheet size detector to obtain a size of a recording sheet on which an image is to be formed by passing through the rotary member;
a drive controller to control driving of the first demagnetizing coil; and
a second demagnetizing coil layered on the excitation coil and generating magnetic flux in a direction reverse to and cancelling out the magnetic flux that the excitation coil generates,
wherein the drive controller drives the first demagnetizing coil after information including the sheet size has been obtained, and
wherein the second demagnetizing coil is disposed opposite the center portion in the axial direction of the rotary member, and the drive controller obtains the information of the recording sheet to be passed through the rotary member including the sheet size information and controls to drive the second demagnetizing coil.

2. A fixing device comprising:
a rotary member including a heat generation layer;
an excitation coil generating magnetic flux, disposed along an axial direction of the rotary member, to heat by induction the heat generation layer of the rotary member;
a first demagnetizing coil layered on the excitation coil and generating magnetic flux in a direction reverse to and cancelling out the magnetic flux that the excitation coil generates;
a sheet size detector to obtain a size of a recording sheet on which an image is to be formed by passing through the rotary member;
a drive controller to control driving of the first demagnetizing coil; and
a second demagnetizing coil layered on the excitation coil and generating magnetic flux in a direction reverse to and cancelling out the magnetic flux that the excitation coil generates,
wherein the drive controller drives the first demagnetizing coil after information including the sheet size has been obtained,
wherein the second demagnetizing coil is disposed opposite the center portion in the axial direction of the rotary member, and the drive controller obtains the information of the recording sheet to be passed through the rotary member including the sheet size information and controls to drive the second demagnetizing coil; and
wherein the drive controller selects the second demagnetizing coil when it is determined that the sheet size obtained in a current image forming process is larger than the sheet size obtained in a previous image forming process.

3. The fixing device as claimed in claim 1 , wherein:
the drive controller further comprises a demagnetizing coil selector;
multiple first demagnetizing coils are disposed at opposite lateral ends in an axial direction of the rotary member; and
the demagnetizing coil selector selects the first demagnetizing coil disposed opposite a non-sheet-passing area through which the recording sheet does not pass based on a size of the recording sheet obtained by the sheet size detector.

4. The fixing device as claimed in claim 3 , wherein the demagnetizing coil selector obtains the non-sheet-passing area from a difference between a length of the rotary member in the rotary axis direction and a widthwise length of the recording sheet obtained by the sheet size detector.

5. The fixing device as claimed in claim 3 , wherein each of the multiple first demagnetizing coils has external dimensions in the axial direction of the rotary member that differ from any other first demagnetizing coil.

6. The fixing device as claimed in claim 3 , wherein the demagnetizing coil selector obtains image data related to an image formed on the recording sheet and selects the first demagnetizing coil disposed opposite an unused area of the recording sheet where no image is formed based on the image data.

7. An image forming apparatus comprising a fixing device as claimed in claim 1 .

8. The fixing device as claimed in claim 2 , wherein:
the drive controller further comprises a demagnetizing coil selector;
multiple first demagnetizing coils are disposed at opposite lateral ends in an axial direction of the rotary member; and
the demagnetizing coil selector selects the first demagnetizing coil disposed opposite a non-sheet-passing area through which the recording sheet does not pass based on a size of the recording sheet obtained by the sheet size detector.

9. The fixing device as claimed in claim 8 , wherein the demagnetizing coil selector obtains the non-sheet-passing area from a difference between a length of the rotary member in the rotary axis direction and a widthwise length of the recording sheet obtained by the sheet size detector.

10. The fixing device as claimed in claim 8 , wherein each of the multiple first demagnetizing coils has external dimensions in the axial direction of the rotary member that differ from any other first demagnetizing coil.

11. The fixing device as claimed in claim 8 , wherein the demagnetizing coil selector obtains image data related to an image formed on the recording sheet and selects the first demagnetizing coil disposed opposite an unused area of the recording sheet where no image is formed based on the image data.

12. An image forming apparatus comprising a fixing device as claimed in claim 2 .

Assignees

• Morisawa Naoko
• Matsusaka Susumu
• Hasegawa Motokazu
• Isoe Yukari
• Ricoh Co Ltd

Inventors

• Morisawa Naoko
• Matsusaka Susumu
• Hasegawa Motokazu
• Isoe Yukari

Classifications

• G03G2215/0132

  vertical medium transport path at the secondary transfer · CPC title

• G03G15/2042

  specially for the axial heat partition · CPC title

• G03G15/80

  Details relating to power supplies, circuits boards, electrical connections · CPC title

• G03G15/2053 Primary

  Structural details of heat elements, e.g. structure of roller or belt, eddy current, induction heating · CPC title