Fixing device and image forming apparatus

Abstract

A fixing device includes a heated body of a hollow cylindrical shape that is made of a conductive material and driven to rotate about an axis center, and a coil that heats the heated body by means of induction heating. The coil is formed of plural coil elements divided in an axial direction of the coil parallel to a rotational axis direction of the heated body, and the coil elements are aligned in such a manner that directions of magnetic fields of adjacent coil elements are opposite to each other. The heated body is set stationary in the rotational axis direction and the coil is reciprocally driven in the axial direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view when viewed in a cross-sectional transverse plane to schematically describe the internal structure of an image forming apparatus (printer) to which a fixing device of the invention is applied.

FIGS. 2A and 2B are views showing the configuration of a fixing device according to a first embodiment of the invention, FIG. 2A being a schematic perspective view and FIG. 2B being a cross section taken on line IIB-IIB of FIG. 2A.

FIG. 3 is a sectional explanatory view showing a major configuration of a reciprocal driving mechanism in the fixing device of the first embodiment.

FIGS. 4A and 4B are explanatory views showing a temperature distribution in a heated body of the fixing device, FIG. 4A showing a temperature distribution of a fixing device in the related art and FIG. 4B showing a temperature distribution of the fixing device according to the first embodiment of the invention.

FIG. 5 is a sectional explanatory view showing a major configuration of a reciprocal driving mechanism in a fixing device according to a second embodiment of the invention.

FIG. 6 is a cross section showing the configuration of a fixing device according to a third embodiment of the invention.

FIG. 7 is a cross section showing the configuration of a fixing device according to a fourth embodiment of the invention.

Claims

1. A fixing device, comprising: a heated body of a hollow cylindrical shape that is made of a conductive material and driven to rotate about an axis center; anda coil that heats the heated body by means of induction heating,wherein:the coil is formed of plural coil elements divided in an axial direction of the coil parallel to a rotational axis direction of the heated body, and the coil elements are aligned in such a manner that directions of magnetic fields of adjacent coil elements are opposite to each other; andthe heated body is set stationary in the rotational axis direction and the coil is reciprocally driven in the axial direction.

2. The fixing device according to claim 1, wherein: the coil is provided concentrically with the heated body inside the heated body.

3. The fixing device according to claim 1, wherein: the coil elements are linked to one another with linking members formed of a ring-shaped magnetic body whose outer peripheral surface is close to an inner peripheral surface of the heated body.

4. The fixing device according to claim 1, wherein: the heated body is a heat roller of a cylindrical shape.

5. The fixing device according to claim 1, wherein: the heated body is an endless heating belt.

6. An image forming apparatus, comprising: an image forming portion configured to apply transfer processing of a toner image to a recording sheet;a fixing portion configured to apply fixing processing to the recording sheet onto which the toner image has been transferred; andan apparatus main body that accommodates the image forming portion and the fixing portion,wherein the fixing portion includes:a heated body of a hollow cylindrical shape that is made of a conductive material and driven to rotate about an axis center; anda coil that heats the heated body by means of induction heating, andwherein:the coil is formed of plural coil elements divided in an axial direction of the coil parallel to a rotational axis direction of the heated body, and the coil elements are aligned in such a manner that directions of magnetic fields of adjacent coil elements are opposite to each other; andthe heated body is set stationary in the rotational axis direction and the coil is reciprocally driven in the axial direction.

7. The image forming apparatus according to claim 6, wherein: the coil is provided concentrically with the heated body inside the heated body.

8. The image forming apparatus according to claim 6, wherein: the coil elements are linked to one another with linking members formed of a ring-shaped magnetic body whose outer peripheral surface is close to an inner peripheral surface of the heated body.

9. The image forming apparatus according to claim 6, wherein: the heated body is a heat roller of a cylindrical shape.

10. The image forming apparatus according to claim 6, wherein: the heated body is an endless heating belt.

11. The image forming apparatus according to claim 6, further comprising: an axis center body that penetrates through a hollow portion of the coil to fixedly support the coil;two coil supporting plates that hold the axis center body on both sides in such a manner that the axis center body is allowed to move in an axial direction thereof;a biasing member that is provided in a space between one wall surface of the apparatus main body and one end portion of the axis center body and confers a biasing force to the one end portion in a direction to cause the coil to move apart from the one wall surface; anda cam member that is provided to the other side wall of the apparatus main body and has an abutting surface on which the other end portion of the axis center body abuts,wherein:the abutting surface undergoes displacement in the axial direction as the cam member is rotationally driven, so that the coil is biased by the abutting surface and reciprocally driven in the axial direction.

12. The image forming apparatus according to claim 6, further comprising: an axis center body that penetrates through a hollow portion of the coil to fixedly support the coil;two coil supporting plates that hold the axis center body on both sides in such a manner that the axis center body is allowed to move in an axial direction thereof;an engagement groove that is carved in a side surface of one end portion of the axis center body; andan engaging member that is provided to one side wall of the apparatus main body and engaged in the engagement groove,wherein:the coil is reciprocally driven in the axial direction in response to a quantity of displacement in the axial direction of the engagement groove in which the engaging member is engaged as the axis center body is rotationally driven.