JP2010049154A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which achieves constitution having a high degree of freedom in adjustment of induction heating object width in a member to be heated with simple constitution, and an image forming apparatus. <P>SOLUTION: A cylindrical center core 55 arranged to be opposed to the member to be heated through a hollow part of an induction coil wound in a width direction of the member to be heated has notched parts 55a formed in an oblique direction from both ends in a longitudinal direction to the ends in the minimum width in a predetermined range set in advance (for example, a range from the maximum paper passing width to the minimum paper passing width), whereby magnetic flux width acting on the member to be heated from the induction coil is consecutively fluctuated within the predetermined range according as the center core 55 is rotated by a core drive mechanism. <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 more particularly to a technique for changing the width of a heating target region of a member to be heated (such as a fixing roller) to be heated by induction. .

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 heated member such as a fixing roller by electromagnetic induction. Specifically, in the fixing device, an induction coil and a magnetic core are disposed so as to face the maximum sheet passing area of a heated member made of a magnetic material. A magnetic flux is generated by passing a high-frequency current through the induction coil. As a result, the magnetic flux generated by the induction coil is guided to the member to be heated through the magnetic circuit formed by the magnetic core, and the member to be heated is heated by the eddy current (induction current) generated by electromagnetic induction by the magnetic flux. The
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 region near the end of the heated member through which the sheet does not pass. Therefore, a configuration in which the width of the heating target region in the heated member can be changed according to the paper size has been studied.
For example, in the fixing device disclosed in Patent Document 1, the plurality of magnetic cores are rotatably arranged so 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.
JP 2005-308783 A

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.
Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to fix a configuration with a high degree of freedom in adjusting the induction heating target width of a member to be heated with a simple configuration. An apparatus and an image forming apparatus are provided.

In order to achieve the above object, the present invention provides an induction coil wound in the width direction of a member to be heated, and a cylindrical first magnetic member disposed opposite to the member to be heated via a hollow portion of the induction coil. A body core, a second magnetic core forming a magnetic circuit that passes outside the induction coil between the heated member and the first magnetic core, and the first magnetic core is rotated. Core rotating means, and guides the member to be heated by guiding the magnetic flux generated by the power supply to the induction coil to the member to be heated by the first magnetic core and the second magnetic core. The present invention is applied to a heating fixing device, and the magnetic flux width acting on the member to be heated from the induction coil as the first magnetic core is rotated by the core rotating means, Within a predetermined range Configured to become a continuous shape that vary as a fixing device according to claim.
More specifically, the first magnetic core is formed with an oblique cutout from one end or both ends in the longitudinal direction to the end of the minimum width in the predetermined range. It is conceivable that the width of the surface has a shape that continuously varies in the circumferential direction within the predetermined range.
In the fixing device configured as described above, the member to be heated is rotated by the first magnetic core and the second magnetic core by rotating the first magnetic core by the core rotation driving unit. Since the width of the magnetic flux guided to can be arbitrarily changed, the degree of freedom in adjusting the width of the object to be heated in the heated member is high, and it is possible to cope with various paper sizes.
For example, the heating range of the heated member can be adjusted within the range of the paper size by setting the predetermined range to a range of the maximum width and the minimum width of the paper size that is passed through the fixing device.
In addition, it is preferable that the apparatus further includes a rotation amount control unit that controls a rotation amount of the first magnetic core by the core rotation unit according to a sheet size to be 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, in the fixing device configured as described above, the first magnetic core and the second magnetic body are rotated by rotating the first magnetic core by the core rotation driving unit. Since the magnetic flux width guided to the heated member by the core can be arbitrarily changed, the degree of freedom of adjustment of the induction heating target width in the heated member is high, and it is possible to cope with various paper sizes. .

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 a copying machine X according to an embodiment of the present invention, FIG. 2 is a schematic diagram showing a schematic configuration of a fixing device 5 according to the embodiment of the present invention, and FIG. FIG. 5 is a schematic diagram for explaining an example of the shape of a center core 55 provided in the fixing device 5 according to the embodiment of the present invention.
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, peripheral devices such as a ROM and a RAM, and executes the process according to a predetermined program stored in the ROM while developing the copy machine X on the RAM. Control all over.
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.

As shown in FIG. 2, the fixing device 5 includes a fixing roller 51 and a pressure roller that rotate while pressing a sheet conveyed on the sheet conveying path 50 after the toner image is transferred in the image forming unit 4. A heating roller 53 (an example of a member to be heated) that is rotationally driven by a driving force transmitted from the fixing roller 51 via a fixing belt 52 stretched between the fixing roller 51 and the fixing roller 51; An induction coil 54 for inductively heating the roller 53, a center core 55 (an example of a first magnetic core) that forms a magnetic circuit that guides the magnetic flux generated by the heating roller 53 to the induction coil 54, and an external core 56 (An example of a second magnetic core).
The fixing roller 51 is connected to driving means such as a stepping motor (not shown), and is rotationally driven by the driving means. When the fixing roller 51 is rotationally driven, the fixing belt 52 travels by the driving force, and the heating roller 53 rotates by the driving force transmitted from the fixing belt 52.
The heating roller 53 is made of a magnetic material such as iron or a magnetic shunt alloy.

The induction coil 54 is wound in the direction of the rotation axis (the depth direction in FIG. 2), which is the width direction of the heating roller 53, and has a longitudinal width (substantially the same as the maximum sheet passing width). The width is substantially the same as the width.
The center core 55 and the outer core 56 are made of a ferromagnetic material such as ferrite, and a magnetic circuit for guiding the magnetic flux generated by the induction coil 54 to the heating roller 53 (see the thick arrow in FIG. 2). ).
In the fixing device 5, the magnetic flux generated in the induction coil 54 by supplying power to the induction coil 54 is guided to the heating roller 53 by the center core 55 and the outer core 56, and the surface of the heating roller 53 is swirled. When the current (inductive current) is generated, the heating roller 53 is heated. As a result, the fixing belt 52 is heated by the heat transfer from the heating roller 53, and the adhering toner is melted and fixed on the paper contacting the fixing belt 52. It is also conceivable that the fixing belt 52 is made of a magnetic member and the fixing belt 52 is directly heated. Further, the fixing roller 51 may be directly induction-heated without the heating roller 53 or the fixing belt 52. In this case, the fixing belt 52 and the fixing roller 51 correspond to a member to be heated.

The outer core 56 is composed of a pair of U-shaped and inverted U-shaped magnetic cores surrounding both sides of the heating roller 53 and the center core 55, and the heating roller 53 and the center core. A magnetic circuit passing through the outside of the induction coil 54 is formed between 55 and 55. The outer core 56 is formed over the entire length in the longitudinal direction of the heating roller 53 and the center core 55, or at predetermined intervals over the entire width in the longitudinal direction of the heating roller 53 and the center core 55. It has a plurality of plate-like cores arranged.
On the other hand, the center core 55 is a cylindrical roller member disposed to face the heating roller 53 through a hollow portion of the induction coil 54, and a magnetic member is provided between the outer core 56 and the heating roller 53. A circuit is formed. The center core 55 is rotatably supported by a core rotation mechanism (not shown) that drives the center core 55 to rotate independently of the heating roller 53. Here, the core rotating mechanism (not shown) is an example of the core rotating means.
The core rotation mechanism (not shown) includes a transmission system such as a rotation shaft and a gear connected to the center core 55, and a drive system such as a stepping motor and a servo motor connected to the rotation shaft and the gear. Yes. The presence / absence of drive of the core rotation mechanism (not shown), the drive amount, and the like are controlled by the control unit 6 and the like. Specifically, when the drive system is a stepping motor that rotates by a predetermined amount in accordance with the number of input steps, the rotation amount of the center core 55 can be controlled by the number of steps input to the stepping motor. it can. The drive system may be configured using, for example, a clutch or a solenoid.
Further, as the center core 55 is rotated by the core rotation mechanism (not shown), the magnetic flux width acting on the heating roller 53 from the induction coil 54 is continuously within a predetermined range. It has a shape that fluctuates. Hereinafter, a specific example will be described with reference to FIG.

3A is a perspective view of the center core 55, and FIGS. 3B to 3D are plan views showing rotational transitions of the center core 55. FIG.
As shown in FIG. 3, the center core 55 has a maximum width and a minimum width range (an example of a predetermined range, hereinafter referred to as “pass-through”) from both ends in the longitudinal direction. An oblique cutout 55a is formed over the end of the minimum width in the “paper range”. That is, the notch 55a is obtained by obliquely cutting both ends of the center core 55 formed in a cylindrical shape. Therefore, as the center core 55 rotates, the center core 55 has a shape in which the width of the outer peripheral surface continuously varies in the circumferential direction within the sheet passing range. For example, when the paper size used in the copying machine X is A3 to B5, the cutout portion 55a is formed so that the A3 size has the maximum width and the B5 size has the minimum width.

Specifically, in the fixing device 5, the upper width of the center core 55 in FIG. 3 is shown in FIGS. 3B to 3D every time the center core 55 is rotated 90 °. Thus, the minimum sheet passing width gradually changes from the maximum sheet passing width. The minimum value of the change width is caused by the resolution of the rotation amount control by the core driving mechanism (not shown) that rotates the center core 55.
Accordingly, in the fixing device 5 configured as described above, the width of the portion facing the heating roller 53 on the circumferential surface of the center core 55 is continuously changed as the center core 55 is driven to rotate. As a result, the width of the magnetic circuit formed by the center core 55 and the outer core 56, that is, the width of the magnetic flux acting on the heating roller 53 can be continuously varied.

In the copying machine X, when the copying process is executed, the control unit 6 passes the driving amount of the core rotating mechanism (not shown), that is, the rotating amount of the center core 55 to the fixing device 5. By controlling according to the paper size to be controlled, overheating of the non-sheet passing area is prevented. The said control part 6 when performing this control processing corresponds to a rotation amount control means. Instead of the control unit 6, the process may be executed by an individual control circuit provided in the fixing device 5. In this case, the control circuit corresponds to a rotation amount control means. .
Specifically, the control unit 6 includes a rotation amount of a drive system such as a stepping motor provided in the core rotation mechanism (not shown) and the center core 55 rotated by the core rotation mechanism (not shown). The relationship with the rotational position is stored, and the width of the portion facing the heating roller 53 on the circumferential surface of the center core 55 is varied by controlling the amount of rotation of the drive system based on the relationship. It is possible. For example, when the size of the paper used in the copying process is A4, the control unit 6 adjusts the rotational position of the center core 55 so that the magnetic flux width acting on the heating roller 53 becomes the A4 size width. . 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 in the copying process and the rotation amount by the core rotation mechanism (not shown), for example, the core rotation mechanism (not shown) for rotating the center core 55 to a position corresponding to the paper size. The driving amount (number of steps, driving time, etc.) to rotate the stepping motor shown in the drawing may be stored in advance in a ROM or the like provided in the control unit 6. Of course, another embodiment is conceivable in which a sensor for detecting the rotational position of the center core 55 is arranged and the amount of rotation of the center core 55 is controlled based on the detection result of the sensor.
When the center core 55 is set at a position corresponding to the paper size in this way, when an alternating current is applied to the induction coil 54, the magnetic flux generated in the induction coil 54 is changed to the paper on the heating roller 53. Only the region corresponding to the width of the size A4 will act, and only the region will be induction heated.

As described above, in the fixing device 5, the center core 55 is rotated by the core rotation mechanism (not shown), thereby the width of the magnetic path formed by the fixing device 5, that is, in the heating roller 53. The width of the target area for induction heating can be arbitrarily changed within a predetermined range between the maximum sheet passing width and the minimum sheet passing width. For example, it appropriately corresponds to any non-standard size set by the user. It is possible.
In the present embodiment, the case where the center of the sheet is passed along the longitudinal center of the heating roller 53 in the fixing device 5 has been described as an example. The cutout portions 55a are provided at both ends, but when one end portion of the paper is passed along one end portion in the longitudinal direction of the heating roller 53, it is opposite to the one end portion. The cutout portion 55a may be provided so as to extend from the end portion to a predetermined range.

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. FIG. 5 is a schematic diagram for explaining an example of the shape of a first magnetic core provided in 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 50 ... Paper conveyance path 51 ... Fixing roller 51a ... Pressure roller 52 ... Fixing belt 53 ... Heating roller (Example of heated member)
54 ... induction coil 55 ... center core (an example of a first magnetic core)
55a ... notch 56 ... outer core (an example of a second magnetic core)
X: Copier (an example of an image forming apparatus)

Claims (5)

An induction coil wound in the width direction of the member to be heated; a cylindrical first magnetic core disposed opposite to the member to be heated through a hollow portion of the induction coil; the member to be heated and the first member A second magnetic core that forms a magnetic circuit that passes outside the induction coil between the first magnetic core and a core rotating means that rotates the first magnetic core;
A fixing device that heats a member to be heated by guiding magnetic flux generated by power supply to the induction coil to the member to be heated by the first magnetic core and the second magnetic core;
As the first magnetic core is rotated by the core rotating means, the magnetic flux width acting on the member to be heated from the induction coil is continuously varied within a predetermined range. A fixing device having a shape.   In the first magnetic core, an oblique cutout is formed from one end or both ends in the longitudinal direction to the end of the minimum width in the predetermined range, so that the width of the outer peripheral surface is circumferential. The fixing device according to claim 1, wherein the fixing device has a shape that continuously varies in a direction within the predetermined range.   The fixing device according to claim 2, wherein the predetermined range is a range of a maximum width and a minimum width of a paper size to be passed through the fixing device.   The rotation amount control means which controls the rotation amount of the said 1st magnetic body core by the said core rotation means according to the paper size passed through the said fixing apparatus is further provided. Fixing device.   An image forming apparatus comprising the fixing device according to claim 1.

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