JP5416940B2 - Fixing device, image forming device - Google Patents

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, Patent Document 1 discloses that the width of the heating target region is changed by changing the width of the magnetic flux acting on the member to be heated from the induction coil with a magnetic flux shielding member.
JP-A-2005-208624

However, if the heating target area of the member to be heated is determined according to the paper size, an area where heating is not originally required becomes a heating target area, and wasteful energy consumption (power consumption) may be performed. For example, if the toner image is transferred only in half of the width direction of the paper and the toner image is not transferred in the other half, assuming that the heating target area of the heated member is the full width of the paper, the toner image The region where no toner is transferred and does not need to be fixed is unnecessarily heated.
Accordingly, the present invention has been made in view of the above circumstances, and its object is to appropriately adjust the width of the heating target region of the heated member according to the transfer position and transfer amount of the toner image on the paper. An object of the present invention is to provide a fixing device and an image forming apparatus capable of suppressing energy consumption.

In order to achieve the above object, the present invention comprises an induction heating means for performing induction heating using a fixing member that melts and fixes toner adhering to a sheet or a heat transfer member that is thermally coupled to the fixing member as a member to be heated, A magnetic flux shielding member provided on a path of magnetic flux acting on the member to be heated from the induction heating means, and having a shape in which the width corresponding to the longitudinal direction of the member to be heated changes in a plurality of stages, A sheet which is applied to a fixing device capable of changing the width of the path of the magnetic flux shielded by the magnetic flux shielding member by moving the magnetic flux shielding member in the plurality of stages, and on which an image is formed transfer position and the toner on to detect the transfer amount of toner for each area corresponding to the width of the plurality of stages on the sheet on which an image is formed, the position and the toner is not transferred, the toner rolling The amount is configured as a fixing device, characterized in that moving the magnetic flux shielding member to shield the path of the magnetic flux corresponding to the region is less than a predetermined amount set in advance.
According to the present invention, the induction heating means acts on the member to be heated by shielding the magnetic flux path corresponding to the position where the toner is not transferred on the paper on which the image is formed and the area where the transfer amount is small. Since the width of the magnetic flux to be adjusted can be adjusted and only the area that needs to be heated in the heated member can be set as the heating target area, wasteful energy consumption can be prevented. This is particularly suitable for printing a plurality of documents on which toner is transferred only in half of the width direction of the paper.
Specifically, the induction heating means includes an induction coil wound in the width direction of the member to be heated, and a cylindrical first magnetic member arranged to face the member to be heated via a hollow portion of the induction coil. It is conceivable to include a body core and a second magnetic core that forms a magnetic circuit that passes outside the induction coil between the heated member and the first magnetic core. In this case, the magnetic flux shielding member is provided on the outer peripheral surface of the first magnetic core, and the first magnetic core is rotated so that the heated member and the first magnetic core are opposed to each other. It is possible to change the width of the magnetic flux path by changing the width of the magnetic flux shielding member.
By the way, the present invention may be understood as an invention of an image forming apparatus including the fixing device configured as described above.

  According to the present invention, the width of the magnetic flux acting on the member to be heated from the induction heating means is adjusted by shielding the magnetic flux path corresponding to the position where the toner is not transferred and the transfer amount is small. Since only the region that needs to be heated in the member to be heated can be set as the region to be heated, wasteful energy consumption can be prevented. This is particularly suitable for printing a plurality of documents on which toner is transferred only in half of the width direction of the paper.

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. It is a schematic diagram for demonstrating the magnetic flux shielding board 60 provided in the fixing apparatus 5 which concerns on embodiment of this 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.
Further, the image processing unit 3 based on the image data, a shielding unit D1 corresponding to a toner transfer position on a sheet on which the image data is formed and a plurality of widths formed on a magnetic flux shielding plate 60 described later. It has a function of detecting the toner transfer amount (printing rate, etc.) and the like for each region of .about.D6 (see the blackened portion in FIG. 3). Here, the image processing unit 3 when executing such detection processing corresponds to toner transfer state detection means. For example, the image processing unit 3 performs detection using a known dot count technique or the like. And the detection result by the said image process part 3 is input into the said control part 6, and is used as a judgment parameter | index in the below-mentioned heating object width change process performed by this control part 6. FIG.

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 relating to the fixing device 5, which will be described in detail below with reference to FIGS. 2 and 3.

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 (heat transfer member, which is rotated by a driving force transmitted from the fixing roller 51 via a fixing belt 52 (an example of a fixing member) stretched between the fixing roller 51 and the fixing roller 51. An example of a member to be heated, an induction coil 54 for induction heating of the heating roller 53, and a center core 55 (a first core) that forms a magnetic circuit that guides the magnetic flux generated by the induction coil 54 to the heating roller 53 An example of a magnetic core) and an outer 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 are formed to have substantially the same width as that of the heating roller 53 in the same manner as the induction coil 54. Has been. The center core 55 and the outer core 56 form a magnetic circuit (see the thick arrow in FIG. 2) that guides the magnetic flux generated by the induction coil 54 to the heating roller 53.
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. Here, the induction coil 54, the center core 55, and the outer core 56 provided for performing induction heating of the heating roller 53 are examples of induction heating means.
When the heating roller 53 is heated, the fixing belt 52 is heated by heat conduction from the heating roller 53 to the fixing belt 52 thermally coupled to the heating roller 53. As a result, on the paper contacting the fixing belt 52, the toner adhering to the paper is melted and fixed. A configuration in which the fixing belt 52 is made of a magnetic member and the fixing belt 52 is directly heated by the magnetic flux from the induction coil 54 is also conceivable. It is also conceivable that the fixing roller 51 is directly induction-heated by the magnetic flux from the induction coil 54 without the heating roller 53 or the fixing belt 52. In these cases, the fixing belt 52 and the fixing roller 51 to be heated correspond to the heated member.

As shown in FIG. 2, 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. A magnetic circuit that passes outside the induction coil 54 is formed between the heating roller 53 and the center core 55.
The outer core 56 is not limited to the one continuously formed over the entire longitudinal width of the heating roller 53 and the center core 55. For example, the outer core 56 is not limited to the longitudinal direction of the heating roller 53 and the center core 55. It may have a plurality of plate-like cores arranged at predetermined intervals over the entire width.

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.
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 a stepping motor that rotates by a predetermined amount according to the number of steps input is used as the drive system, 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, in the fixing device 5, the longitudinal width of the heating roller 53 changes in a plurality of stages on the outer peripheral surface of the center core 55 on the path of the magnetic flux acting on the heating roller 53 from the induction coil 54. A magnetic flux shielding plate 60 (an example of a magnetic flux shielding member) having a shape is provided. The magnetic flux shielding plate 60 is made of a material such as silver, copper, or aluminum that shields the magnetic flux, and rotates as the center core 55 rotates.

Here, the magnetic flux shielding plate 60 will be described with reference to FIG. FIG. 3 is a schematic diagram for explaining the magnetic flux shielding plate 60 and shows a development view of the center core 55 and the magnetic flux shielding plate 60. In FIG. 3, the outer peripheral surface of the center core 55 appears.
As shown in FIG. 3, the magnetic flux shielding plate 60 has shielding portions D1 to D6 (marked portions in FIG. 3) having different positions and widths that shield the magnetic flux path from the center core 55 to the heating roller 53. doing. The magnetic flux shielding plate 60 is divided into two on the left and right sides of the center core 55. Further, the center core 55 has a non-shielding portion D0 where the magnetic flux shielding plate 60 is not provided.
Here, each of the shielding portions D1 to D6 includes, in the center core 55, the right side 2/3, the right side 1/2, the right side 1/3 and the left side 1/3, the left side 1/2, the left side 2/3, the full width, Each has a position and width corresponding to each of the above. Therefore, the exposed region of the center core 55 on the outer peripheral surface of the center core 55 is a region excluding the shielding portions D1 to D6 (the white portions in FIG. 3). In the shielding portions D1 to D6, the center core is exposed. The magnetic flux from 55 is shielded.
Note that the shielding portions D1 to D6 described here are merely examples. For example, when the copying machine X supports various paper sizes such as A3, A4, B4, and B5, the magnetic shielding plate 60 has a width of the various paper sizes and half of each paper size. It is conceivable that a multi-stage shielding portion corresponding to each of the widths is formed. Of course, it may be further subdivided.

In the copying machine X configured as described above, the center core 55 is rotated so that the width of the magnetic flux shielding plate 60 at the facing portion where the heating roller 53 and the center core 55 are closest is the shielding portions D1 to D1. By changing to any one of D6, it is possible to change the position and width of the path of the magnetic flux acting from the center core 55 to the heating roller 53, that is, the heating target area of the heating roller 53.
In the copying machine X, the control unit 6 rotates the center core 55 and rotates the magnetic flux shielding plate 60 in accordance with the transfer state of toner on the sheet on which image formation is performed. A magnetic flux width changing process for adjusting the heating target area of the heating roller 53 is executed. The said control part 6 when performing the magnetic flux width change process which concerns here corresponds to a magnetic flux width change means. Hereinafter, a specific example of the magnetic flux width changing process will be described.

First, when the image forming process is requested in the copying machine X, the control unit 6 detects the image data corresponding to the image formed on the paper by the image forming process by the image processing unit 3. The toner transfer position and the toner transfer amount (printing rate, etc.) for each of the shielding portions D1 to D6 are acquired from the image processing unit 3.
Based on the detection result acquired from the image processing unit 3, the control unit 6 determines that each of the shielding units D <b> 1 to D <b> 6 is an area where heating is not necessary on the heating roller 53 (hereinafter referred to as “heating unnecessary area”). It is determined whether or not it corresponds to the above. Specifically, the control unit 6 determines whether the toner is not transferred to a position on the paper (half the paper width) corresponding to each of the shielding units D1 to D6, or on the paper corresponding to each of the shielding units D1 to D6. When the toner transfer amount in the range is equal to or less than a predetermined amount set in advance, it is determined that the shielding portions D1 to D6 correspond to the heating unnecessary region.
Further, for example, it is determined whether or not the shielding portions D1 to D6 are the heating unnecessary regions in a wide order of shielding regions or in a preset order, and the detection process is terminated when the heating unnecessary region is detected. It is also conceivable as another embodiment. Thereby, a process can be complete | finished when it determines with the shielding part with high priority among the said shielding parts D1-D6 being the said heating unnecessary area | region.

The determination of the necessity of heating each of the shielding portions D1 to D6 is based on the relationship between the temperature of the heating roller 53 and the fixing belt 52 detected by a temperature sensor such as a thermistor provided in the fixing device 5. It may be considered.
Specifically, a configuration for determining the necessity of heating each of the shielding portions D1 to D6 depending on whether or not the printing rate in the range on the paper corresponding to each of the shielding portions D1 to D6 is equal to or less than a preset threshold value. in the case the temperature detected by said temperature sensor is high, it is considered that the said threshold than when the detected temperature by the low temperature sensor is set to higher due so. Thereby, for example, when the printing rate is low and the toner transferred to the sheet is small enough to be fixed by the residual heat of the fixing belt 52, the magnetic flux from the center core 55 to the heating roller 53 is reduced. By interposing the shielding portion D6 of the magnetic flux shielding plate 60 on the path, it is possible to control so as not to heat the heating roller 53 by shielding the magnetic flux to the entire width of the heating roller 53. Consumption can be saved.

When the control unit 6 determines that any one of the shielding units D1 to D6 corresponds to the heating unnecessary region, the control unit 6 determines that the shielding unit is determined as the heating unnecessary region. Among the cores D1 to D6, the center core 55 is shielded by the core rotation mechanism (not shown) so that the shield part having the widest shield area is interposed in the facing part where the center core 55 and the heating roller 53 are closest. And the magnetic flux shielding plate 60 is rotated.
As a result, the center core 55 is located at a position where the toner detected by the image processing unit 3 is not transferred or an area where the toner transfer amount detected by the image processing unit 3 is equal to or less than a predetermined amount. Therefore, the path of the magnetic flux acting on the heating roller 53 is shielded. For example, when a toner image is formed only on half of an A3 size sheet, the path of magnetic flux corresponding to the remaining half area except the half area is shielded.
The rotational movement amount of the magnetic flux shielding plate 60 is adjusted by the number of steps input to a stepping motor provided in the core rotation mechanism (not shown) that rotationally drives the center core 55. Specifically, the control unit 6 includes a rotation amount of a drive system such as the stepping motor stored in advance in a ROM or the like of the control unit 6 and the center core 55 rotated by the core rotation mechanism (not shown). The amount of rotation of the drive system is controlled based on the relationship with the rotational position. Of course, a sensor for detecting the rotation position of the center core 55 or the magnetic flux shielding plate 60 may be arranged, and the rotation amount of the center core 55 may be controlled based on the detection result by the sensor.

Thus, in the fixing device 5, the shielding area of the magnetic path between the center core 55 and the heating roller 53 is any one of the shielding portions D 1 to D 6 of the magnetic flux shielding plate 60 positioned on the magnetic path. Therefore, the position and width corresponding to the heating unnecessary region are set.
Therefore, after that, when an alternating current is applied to the induction coil 54, the magnetic flux generated by the induction coil 54 does not act on the area corresponding to the heating unnecessary area on the heating roller 53, and the heating unnecessary. Since induction heating is performed by acting only on a region that requires heating excluding the region, it is possible to prevent wasted energy from being consumed to heat the region that does not require heating. In particular, such a configuration is suitable for printing a plurality of documents on which toner is transferred only in half of the width direction of the paper.

On the other hand, when the controller 6 determines that not all of the shielding portions D1 to D6 correspond to the heating unnecessary region, the entire width of the heating roller 53 needs to be heated. Therefore, in this case, the control unit 6 is configured so that the non-shielding portion D0 of the center core 55 is interposed in the opposite portion where the center core 55 and the heating roller 53 are closest to each other. ) To rotate the center core 55.
Thereby, in the fixing device 5, a magnetic flux path is established between the entire width of the center core 55 and the entire width of the heating roller 53, and the entire heating roller 53 can be heated.

In this embodiment, the description has been made on the assumption that the sheet is conveyed so that the center of the sheet is aligned with the center of the fixing belt 52 in the width direction. The present invention is also applicable to a configuration in which the paper is conveyed so that one end of the paper is along one end.
Further, in the present embodiment, the magnetic flux shielding plate 60 is provided along the outer peripheral surface of the center core 55, and the shielding width of the path of the magnetic flux acting on the heating roller 53 from the center core 55 by rotational movement. The case of changing is described as an example, but is not limited thereto. For example, in a configuration in which the center core 55 and the heating roller 53 are slidable in the width direction of the heating roller 53, the magnetic flux path from the center core 55 to the heating roller 53 is blocked by the sliding movement. The structure which can change a width | variety may be sufficient.

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. 4 is a schematic diagram for explaining a magnetic flux shielding member 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 (An example of a toner transfer state detection means)
4 ... Image forming section 5 ... Fixing device 6 ... Control section 50 ... Paper transport path 51 ... Fixing roller 51a ... Pressure roller 52 ... Fixing belt (an example of a fixing member)
53 ... Heating roller (an example of a heat transfer member and a member to be heated)
54 ... induction coil 55 ... center core (an example of a first magnetic core)
56 ... External core (an example of a second magnetic core)
60 ... Magnetic flux shielding plate (an example of magnetic flux shielding member)
D0: Non-shielding parts D1-D6 ... Shielding part X ... Copying machine (an example of an image forming apparatus)

Claims (3)

An induction heating unit that performs induction heating using a fixing member that melts and fixes the toner adhering to the sheet or a heat transfer member that is thermally coupled to the fixing member as a member to be heated, and the induction heating unit that acts on the member to be heated. A magnetic flux shielding member provided on a path of the magnetic flux to be heated and having a shape in which the width corresponding to the longitudinal direction of the heated member changes in a plurality of stages, and the magnetic flux shielding member is shielded by moving the magnetic flux shielding member. A magnetic flux width changing means for changing the width of the magnetic flux path to the plurality of stages,
Be provided with a toner transfer state detecting means for detecting the transfer amount of toner for each area corresponding to the width of the plurality of stages on paper images are formed,
The flux width changing means, said magnetic flux shielding member to shield the path of the magnetic flux transfer amount of toner detected by the previous SL toner transfer state detecting means corresponds to a region equal to or less than a predetermined amount set in advance It moved so Rutotomoni, is to shall increase the predetermined amount set value in comparison with the case where the temperature detected by the temperature sensor in the member to be heated is lower than the detected temperature the predetermined value is higher than a predetermined value A fixing device. The induction heating means includes an induction coil wound in a width direction of the member to be heated, a cylindrical first magnetic core disposed opposite to the member to be heated via a hollow portion of the induction coil, A second magnetic core that forms a magnetic circuit that passes outside the induction coil between the heated member and the first magnetic core;
The magnetic flux shielding member is provided on the outer peripheral surface of the first magnetic core, and the magnetic flux width changing means rotates the first magnetic core to rotate the heated member and the first magnetic core. The fixing device according to claim 1, wherein a width of the magnetic flux path is changed by changing a width of the magnetic flux shielding member at a facing portion of one magnetic core. An image forming apparatus comprising the fixing device according to claim 1.

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