JP2009288634A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus wherein a high flexibility of width adjustment of a target region to be heated by induction heating is achieved by a simple configuration. <P>SOLUTION: A fixing device 5 includes a hollow cylindrical heating roller 53 made of a non-magnetic material, an induction coil 71 and a magnetic core 72 disposed in opposition to each other on the outside of the heating roller 53, a magnetic core 81 disposed in the heating roller 53 so that a surface of the heating roller 53 is interposed between the induction coil 71 and the magnetic core 72, and a core rotating mechanism 10 for rotationally driving the magnetic core 81 independently of the heating roller 53. The magnetic core 81 has such a shape that its width facing the induction coil 71 and the magnetic core 72 is continuously varied between a maximum paper passage area and a minimum paper passage area of the heating roller 53 in accordance with rotational driving by the core rotating mechanism 10. Thus a target area to be heated of the heating roller 53 is changed by the rotation position of the magnetic core 81. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an induction heating type fixing device and an image forming apparatus including the same, and in particular, adjusts the width of a heating target region where induction heating is performed in a fixing roller or a heating roller thermally coupled to the fixing roller. For technology.

In general, an image forming apparatus such as a printer, a copying machine, a facsimile machine, or a multifunction machine of these uses an induction heating type fixing device that heats a fixing roller by electromagnetic induction. Specifically, in the fixing device, an induction coil is disposed so as to face a maximum sheet passing area of a fixing roller made of a magnetic member, and a magnetic flux is generated by passing an alternating current through the induction coil. As a result, the fixing roller is heated by eddy current (inductive current) generated by electromagnetic induction by the magnetic flux from the induction coil.
Conventionally, in such an induction heating type fixing device, when a paper having a size smaller than the maximum paper passing area is passed, in order to maintain the paper passing area through which the paper passes at a predetermined fixing temperature, There is a problem that overheating occurs in a non-sheet passing area near the end of the fixing roller through which the sheet does not pass. Therefore, a configuration in which the width of the heating target area in the fixing roller can be changed according to the sheet size has been studied.
For example, in the fixing device disclosed in Patent Document 1, the plurality of magnetic cores are rotatably arranged such that any one of the plurality of magnetic cores having different lengths faces the induction coil. In such a configuration, the width of the heating target region of the member to be heated can be changed by changing the magnetic core corresponding to the induction coil.
Further, in the fixing device disclosed in Patent Document 2, the width of the magnetic circuit formed between the induction coil and the magnetic core is changed by blocking the magnetic flux acting on the fixing roller from the induction coil with the magnetic flux shield. However, the heating target area of the fixing roller is changed.
JP 2005-308783 A Japanese Patent No. 3624040

However, the configuration of Patent Document 1 has a problem that in order to cope with various paper sizes, a large number of magnetic cores having different lengths are required for each paper size. Further, even if a large number of magnetic cores are provided according to the paper size standards, it is not possible to cope with finer settings, for example, arbitrary size settings by the user.
On the other hand, in the configuration of Patent Document 2, it is not possible to cope with a plurality of paper sizes because only switching whether or not to shield with the magnetic shield is performed. Even if a magnetic shielding plate corresponding to each of a plurality of paper sizes is prepared, in that case, the configuration becomes complicated, which is not practical.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fixing device and an image forming apparatus that realize a configuration with a high degree of freedom in adjusting the width of a heating target region by induction heating with a simple configuration. To provide an apparatus.

In order to achieve the above object, the present invention is a hollow cylindrical member to be heated made of a non-magnetic material, and is disposed outside the member to be heated and opposed to the maximum sheet passing area on the surface of the member to be heated. An induction coil including an induction coil, and heating the member to be heated by applying a magnetic flux to the member to be heated; and the surface of the member to be heated is interposed between the induction heating unit and the induction heating unit. A magnetic circuit is disposed inside the heated member so as to face the maximum sheet passing region on the surface of the heated member, and forms a magnetic circuit that passes from the induction heating unit through the heated member and returns to the induction heating unit. And a rotation drive means for rotating the magnetic core independently of the member to be heated, the magnetic core comprising the magnetic core. For rotational drive means The width opposed to the induction heating means has a shape that continuously varies between the maximum sheet passing area and the minimum sheet passing area in the heated member in accordance with the rotational driving. Configured as a fixing device. For example, it can be considered that it has a substantially trapezoidal shape when viewed from the circumferential direction of the member to be heated.
In the fixing device configured as described above, the magnetic member core is rotated by the rotation driving unit, thereby changing the width of the induction heating unit and the magnetic core opposite to each other, thereby heating the member to be heated. The width of the target area can be arbitrarily changed, and various paper sizes can be handled.
More specifically, it is desirable to further include a rotation amount control means for controlling the rotation amount of the magnetic core by the rotation driving means in accordance with the paper size passed through the fixing device. Accordingly, it is possible to automatically adjust the heating target area in the heated member according to the paper size, and to prevent an excessive temperature rise at the end of the heated member.
Incidentally, the present invention can also be understood as an invention of an image forming apparatus provided with the fixing device.

  According to the present invention, the width of the heating target region in the heated member can be arbitrarily changed by changing the width at which the induction heating means and the magnetic core are opposed to each other, which corresponds to various paper sizes. It is possible.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a block diagram showing a schematic configuration of the copying machine X according to the embodiment of the present invention, and FIGS. 2 and 3 are schematic diagrams showing a schematic configuration of the fixing device 5 according to the embodiment of the present invention. is there.
First, a schematic configuration of the copying machine X according to the embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, a copying machine X according to an embodiment of the present invention includes an operation display unit 1, an image reading unit 2, an image processing unit 3, an image forming unit 4, a fixing device 5, a control unit 6, and the like. In general, it is structured. The copying machine X has various other constituent elements that a general electrophotographic copying machine has, but since these are not different from the conventional ones, description thereof is omitted here. The present invention is not limited to the copying machine X, and can also be applied to, for example, an electrophotographic image forming apparatus such as a printer apparatus, a facsimile apparatus, and a multifunction machine having these functions and a scanner function.

The control unit 6 includes a CPU and peripheral devices such as a ROM and a RAM, and controls the copier X in an integrated manner by executing processing according to a predetermined program stored in the ROM.
The operation display unit 1 includes a liquid crystal display that displays various types of information according to instructions from the control unit 6, a touch panel for performing operation input to the control unit 6, and the like.
The image reading unit 2 reads an image of a document set on a document table or an ADF (automatic conveyance device), and the image data read by the image reading unit 2 is input to the image processing unit 3. The
The image processing unit 3 performs various operations on image data of a document read by the image reading unit 2 and image data of a document input from an information processing apparatus (not shown) via a communication network such as a LAN. Image processing is performed. The image data that has been subjected to image processing by the image processing unit 3 is input to the image forming unit 4.
The image forming unit 4 includes a photosensitive drum, a charger, a developing device, an LSU, and the like. A toner image (developer) is applied to a sheet based on image data of a document input from the image processing unit 3. To form.
The fixing device 5 melts and fixes the toner image on the paper on which the toner image is formed by the image forming unit 4. The copying machine X according to the embodiment of the present invention is characterized by the configuration and operation related to the fixing device 5 and will be described in detail below.

FIG. 2 is a schematic diagram showing a side cross-section of the fixing device 5, and FIG. 3 is a schematic diagram of a main part when the heating roller 53 of the fixing device 5 is viewed from the sheet feeding direction. 3A shows the state of the fixing device 5 when heating the maximum sheet passing area, and FIG. 3B shows the state of the fixing device 5 when heating the minimum sheet passing area.
As shown in FIGS. 2 and 3, the fixing device 5 includes a fixing roller 51 that rotates after the toner image is transferred in the image forming unit 4 and rotates while pressing the sheet conveyed on the sheet conveying path 50. A fixing belt comprising a pressure roller 52, a heating roller 53 (an example of a member to be heated) having substantially the same length as the fixing roller 51, and a nonmagnetic member stretched around the fixing roller 51 and the heating roller 53. 54, an induction coil 71 for generating a magnetic flux by energization of an alternating current, an external core 72 and an internal core 81 for forming a magnetic path (magnetic circuit) of the magnetic flux generated by the induction coil 71, and the internal core 81 And a core rotation mechanism 10 (an example of a rotation driving means) that rotatably supports the motor.
The heating roller 53 is an example of a hollow cylindrical heated member made of a nonmagnetic material such as stainless steel (SUS), and the inner core 81 is an example of a magnetic core made of a ferromagnetic material such as ferrite. It is. The outer core 72 is also made of a ferromagnetic material such as ferrite.
In the fixing device 5, a magnetic path (an arrow in FIG. 2) through which the magnetic flux generated in the induction coil 71 passes through the heating roller 53 is formed by the outer core 72 and the inner core 81 that are arranged to face each other. As a result, in the fixing device 5, the heating roller 53 is heated by Joule heat of eddy current generated in the heating roller 53 due to the magnetic flux from the induction coil 71, and is stretched around the heating roller 53. The fixing belt 54 is heated.

By the way, in the copying machine X, since the image forming process (printing process) is executed using various paper sizes, the paper passing area of the fixing belt 54 of the fixing device 5 changes. In the fixing device 5, as shown in FIG. 3, the width of the sheet conveyed on the sheet conveying path 50 is the center in the longitudinal direction of the fixing roller 51 (the line segment P in FIG. 3). -P).
Specifically, in the copying machine X, as shown in FIG. 3, various paper sizes are used in a range from A5 which is the minimum size to A3 which is the maximum size, and the heating roller 53 is set to the maximum size. It shall have a corresponding length. In this case, the sheet passing width of the fixing belt 54 of the fixing device 5 is between the minimum sheet passing area (about 150 mm) corresponding to the A5 size and the maximum sheet passing area (about 300 mm) corresponding to the A3 size. Change.
Here, in the fixing device 5, when the entire area in the longitudinal direction of the heating roller 53 is heated so that the entire area of the fixing belt 54 is always heated regardless of the sheet size, the sheet passing through the fixing belt 54 is performed. In order to maintain the temperature of the region at a predetermined fixing temperature, overheating may occur at both ends of the heating roller 53 corresponding to the non-sheet passing region of the fixing belt. Therefore, when the paper size is smaller than the A3 size corresponding to the maximum paper passing area, the heating target area in the heating roller 53 is limited to the width of the paper passing area corresponding to the paper size. Is desirable.
Therefore, in the fixing device 5 according to the present embodiment, as described later, the width of the heating target region in the heating roller 53 is adjusted by rotating the inner core 81 by the core rotating mechanism 10. This point will be described in detail below.

The induction coil 71 is formed of an electric wire wound with an air core in the axial direction of the heating roller 53 over the maximum sheet passing area on the surface of the heating roller 53. It is arranged outside and at a position spaced apart from the surface of the heating roller 53 by a predetermined distance. The predetermined interval is set in advance as an interval at which a magnetic path can be formed between the induction coil 71 and the outer core 72 and the inner core 81. It is also possible to arrange the induction coil over the maximum sheet passing area by arranging a plurality of induction coils in the longitudinal direction of the heating roller 53 as another embodiment.
The outer core 72 has a substantially U-shape surrounding a part of the heating roller 53 in the circumferential direction, and is disposed outside the heating roller 53 so as to face the maximum sheet passing area of the heating roller 53. ing. In addition, the induction coil 71 is disposed in the surrounding space of the outer core 72.
The outer core 72 passes the magnetic flux generated by the induction coil 71 through the surface of the heating roller 53, passes through the inner core 81, and passes again through the surface of the heating roller 53 (see FIG. 2 arrows). The outer core 72 may be configured by magnetic coupling of a plurality of magnetic cores. In the fixing device 5, the heating roller 53 is induction-heated by causing the magnetic flux generated by the induction coil 71 to act on the heating roller 53 by the external core 72. Here, the induction coil 71 and the outer core 72 are examples of induction heating means.

On the other hand, the inner core 81 is disposed inside the heating roller 53 so as to face the maximum sheet passing area on the surface of the heating roller 53. The inner core 81 is generated by the induction coil 71 and guided by the outer core 72, and the magnetic flux passing through the surface of the heating roller 53 passes through the surface of the heating roller 53 and returns to the outer core 72. This is for forming a magnetic path (arrow in FIG. 2), and is rotatably supported by the core rotation mechanism 10.
The core rotating mechanism 10 rotates the inner core 81 independently of the heating roller 53, and includes rotating shafts 11 and 12 connected to both ends of the inner core 81, and the rotating shaft 12. Rotating gears 13 and 14 connected to each other and a drive motor 15 such as a stepping motor connected to the rotating gear 14 are provided. The rotating shaft 11 is pivotally supported by a casing (not shown) of the fixing device 5 and a casing (not shown) of the copying machine X.
The inner core 81 has a width (a closest width) facing the induction coil 71 and the outer core 72 corresponding to the maximum sheet passing area in the heating roller 53 as the core rotating mechanism 10 rotates. The shape continuously varies from the width of A3 to the width of A5 corresponding to the minimum sheet passing area. Specifically, in the fixing device 5, the inner core 81 has a shape obtained by obliquely cutting off both ends of a cylinder. As shown in FIG. 3, the inner core 81 is viewed from the circumferential direction of the heating roller 53. Are formed in a substantially trapezoidal shape.
Thereby, in the fixing device 5, the width of the magnetic path formed between the inner core 81 and the induction coil 71 and the outer core 72 varies depending on the rotational position of the inner core 81. Accordingly, the width of the magnetic flux penetrating the surface of the heating roller 53 in the longitudinal direction of the heating roller 53 also changes.

In the fixing device 5 configured as above, the control unit 6 controls the drive motor 15 to rotationally drive the inner core 81 by the rotational force transmitted from the rotary gears 14 and 13. The width of the magnetic path formed between the inner core 81 and the induction coil 71 and the outer core 72, that is, the width of the heating target region in the heating roller 53 can be adjusted.
Specifically, the control unit 6 controls the amount of rotation of the internal core 81 according to the paper size passed through the fixing device 5. The said control part 6 when performing this control processing corresponds to a rotation amount control means. Note that the processing may be executed by a control circuit provided in the fixing device 5 instead of the control unit 6, and in this case, the control circuit corresponds to a rotation amount control means.
For example, when the size of the paper used is A4, the control unit 6 causes the induction coil 71, the outer core 72 and the inner core 81 to face each other, that is, the magnetic flux from the induction coil 71 is the inner core. The inner core 81 is rotated so that the width acting on the 81 becomes the width of A4 size. The control unit 6 determines the paper size to be passed to the fixing device 5 from the setting data of the paper for the printing process executed by the copying machine X, the type of the paper feed cassette used in the printing process, and the like. Is detected. Further, the relationship between the paper size used and the amount of rotation by the core rotation mechanism 10, for example, the driving amount (the number of steps and the driving amount) of the driving motor 15 for rotating the internal core 81 to a position corresponding to the paper size. Time etc. may be stored in advance in a ROM or the like provided in the control unit 6. Of course, a sensor for detecting the rotational position of the inner core 81 may be arranged as another embodiment.
In the fixing device 5, when the internal core 81 is set at a position corresponding to the paper size, an alternating current is applied to the induction coil 71, and the heating roller only in the region corresponding to the width of the paper size A 4. 53 induction heating is performed. Accordingly, it is possible to prevent an excessive temperature rise at the end of the heating roller 53 corresponding to the non-sheet passing area of the fixing belt 54. At this time, the magnetic flux generated by the induction coil 71 also passes through the fixing belt 54, and the fixing belt 54 formed of a nonmagnetic material is also directly heated.

As described above, in the fixing device 5, the inner core 81 is rotated by the core rotating mechanism 10, so that the width of the magnetic path formed by the fixing device 5, that is, the heating target region in the heating roller 53 is increased. Can be arbitrarily changed between the maximum sheet passing area (see FIG. 3A) and the minimum sheet passing area (see FIG. 3B). Therefore, the degree of freedom in adjusting the width of the heating target region in the heating roller 53 is high, and it is possible to deal with any size set by the user, for example.
In the present embodiment, the configuration in which the heating roller 53 on which the fixing belt 54 is stretched is inductively heated has been described as an example. However, the present invention is not limited to this, and in the configuration without the fixing belt 54, It is conceivable that the inner core 81 is disposed inside the fixing roller 51 that is in direct contact with the paper, and the fixing roller 51 is directly heated.

In the present embodiment, an example in which the center of the sheet is passed along the longitudinal center of the heating roller 53 (line segment PP in FIG. 3) in the fixing device 5 is taken as an example. As described above, the present invention can be applied even if one end portion of the sheet is passed along one end portion in the longitudinal direction of the heating roller 53.
In this case, for example, as shown in FIG. 4, the inner core 81 is rotated by the core rotating mechanism 10 by making the shape of the inner core 81 into a shape in which only one end of a cylinder is cut obliquely. What is necessary is just to comprise so that the width | variety of the area | region in which this internal core 81 opposes the said induction coil 71 or the said external core 72 by drive may be fluctuate | varied on the basis of the end of this heating roller 53. Thereby, the heating target area of the heating roller 53 in the fixing device 5 is continuously changed between the maximum sheet passing area (see FIG. 4A) and the minimum sheet passing area (see FIG. 4B). It is possible to make it.

1 is a block diagram showing a schematic configuration of a copier according to an embodiment of the present invention. 1 is a schematic diagram illustrating a schematic configuration of a fixing device according to an embodiment of the present invention. 1 is a schematic diagram illustrating a schematic configuration of a fixing device according to an embodiment of the present invention. FIG. 9 is a schematic diagram illustrating another configuration example of the fixing device according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Operation display part 2 ... Image reading part 3 ... Image processing part 4 ... Image forming part 5 ... Fixing device 6 ... Control part 10 ... Core rotating mechanism 11, 12 ... Rotating shafts 13, 14 ... Rotating gear 15 ... Drive motor 50 ... paper transport path 51 ... fixing roller 52 ... pressure roller 53 ... heating roller 54 ... fixing belt 71 ... inductive coil 72 ... outer core 81 ... inner core X ... copier

Claims (4)

A hollow cylindrical heated member made of a non-magnetic material;
An induction coil arranged outside the heated member so as to face the maximum sheet passing area on the surface of the heated member, and heats the heated member by applying a magnetic flux to the heated member Induction heating means;
The surface of the heated member is interposed between the induction heating unit and the induction heating unit so as to be opposed to the maximum sheet passing region on the surface of the heated member. A magnetic core for forming a magnetic circuit passing through the member to be heated and returning to the induction heating means;
A fixing device comprising:
Comprising rotational drive means for rotationally driving the magnetic core independently of the heated member;
A shape in which the width of the magnetic core facing the induction heating unit continuously varies between the maximum sheet passing region and the minimum sheet passing region in the heated member in accordance with the rotation driving by the rotation driving unit. A fixing device comprising:   The fixing device according to claim 1, further comprising a rotation amount control unit that controls a rotation amount of the magnetic core by the rotation driving unit according to a sheet size passed through the fixing device.   The fixing device according to claim 1, wherein the magnetic core has a substantially trapezoidal shape when viewed from a circumferential direction of the heated member.   An image forming apparatus comprising the fixing device according to claim 1.

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