Patent Grant
7369804
The present invention relates to a fixing apparatus useful for employment in an image forming apparatus such as an electrophotographic or electrostatographic copier, facsimile machine, or printer, and more particularly to a fixing apparatus that heat-fixes an unfixed image onto a recording medium using an induction heating type of heating section.
An induction heating (IH) type of fixing apparatus generates an eddy current through the action of a magnetic field generated by a magnetic field generation section in a heat-producing element, and heat-fixes an unfixed image on a recording medium such as transfer paper or an OHP sheet through Joule heating of the heat-producing element by means of the eddy current.
An advantage of this induction heating type of fixing apparatus compared with a heat roller type of fixing apparatus that uses a halogen lamp as a heat source is that heat production efficiency is higher and the fixing speed can be increased.
With a fixing apparatus that uses a thin heat-producing element comprising a thin sleeve or endless belt as the heat-producing element, the thermal capacity of the heat-producing element is low and the heat-producing element can be made to produce heat in a short time, enabling startup responsiveness until heat production at a predetermined fixing temperature to be markedly improved.
On the other hand, with a fixing apparatus that uses this kind of heat-producing element of low thermal capacity, heat is lost simply through the passage of a recording medium, causing a drop in the temperature of the paper passage area. Therefore, with this kind of fixing apparatus, the heat-producing element is heated in a timely fashion so that the temperature of the paper passage area is maintained at a predetermined fixing temperature.
Consequently, with a fixing apparatus that uses this kind of heat-producing element of low thermal capacity, if recording media of small size are fed through continuously, the heat-producing element is continuously heated, and a phenomenon whereby the temperature of a paper non-passage area becomes abnormally higher than the temperature of a paper passage area—that is, a phenomenon of an excessive rise in temperature of a paper non-passage area—occurs.
A known technology for eliminating this kind of phenomenon of an excessive rise in temperature of a paper non-passage area is one whereby, of the magnetic flux generated by a magnetic flux generation section that performs induction heating of the heat-producing element, only magnetic flux that acts on a paper non-passage area of the heat-producing element is absorbed by a magnetic flux absorption member capable of moving in the heat production width direction of the heat-producing element (see, for example, Patent Document 1).
Another known technology for eliminating the phenomenon of an excessive rise in temperature of a paper non-passage area is one whereby a second core of magnetic material corresponding to a paper non-passage area is positioned at the rear of a first core of magnetic material of a magnetic flux generation section that causes heat generation of a heat-producing element by electromagnetic induction, and the lengthwise temperature distribution of the heat-producing element is changed by varying the gap between the first core of magnetic material and second core of magnetic material (see, for example, Patent Document 2).
In
As shown in
When the size of recording material 14 is the maximum size, magnetic flux masking shield 31 is moved by means of displacement section 40 so as to be withdrawn into the position shown by the solid line in
In
Pressure roller 58 rotates in the direction of transportation of recording material 59 while pressing against fixing roller 57 and forming a nip area. By having recording material 59 gripped and transported by means of this nip area, an unfixed image on recording material 59 is heat-fixed to recording material 59 by heated fixing roller 57.
First core 55 has the same width as the width of the maximum paper passage area of fixing roller 57. When the size of recording material 59 is the maximum size, second core 56 is moved to a position close to first core 55, as shown in
However, as the former fixing apparatus has a configuration whereby magnetic flux masking shield 31 is advanced and withdrawn with respect to the gap at either end of coil assembly 10 and holder 12 by means of displacement section 40, there is a problem in that the pair of pulleys 36 of displacement section 40 project greatly from either end of holder 12, as shown in
Furthermore, as shown in
Also, as shown in
Consequently, with this fixing apparatus, diverted flow of magnetic flux from the paper passage area end corresponding to first core 55 to the paper non-passage area end corresponding to second core 56 occurs, and the efficacy of magnetic flux suppression in a paper non-passage area of fixing roller 57 becomes low. As a result, a problem with this fixing apparatus is that when small-sized recording material 59 is fed through continuously, heat is accumulated in a paper non-passage area of fixing roller 57, and an excessive rise in temperature cannot be effectively suppressed.
Also, with this fixing apparatus, only a second core 56 for one recording material size can be held in core-holding rotating member 53, and therefore the paper passage area width of fixing roller 57 can only be made to provide for two recording material paper widths—maximum size and small size.
It is an object of the present invention to provide a small fixing apparatus that can prevent an excessive rise in temperature of a paper non-passage area due to diverted flow of magnetic flux from a paper passage area of a heat-producing element to a paper non-passage area thereof.
A fixing apparatus of the present invention has: a magnetic flux generation section that generates magnetic flux; a heat-producing element that is induction-heated by the magnetic flux; a magnetic path forming element that is positioned opposite the heat-producing element and forms a magnetic flux path between the magnetic flux generation section and the heat-producing element; a magnetism suppressing element that is provided in the magnetic path forming element and, by coming to a masking position that masks at least part of a magnetic flux path corresponding to a paper non-passage area of the heat-producing element between the magnetic path forming element and the heat-producing element, suppresses magnetic coupling between the magnetic path forming element and the heat-producing element, the magnetic coupling being corresponding to the paper non-passage area; and a rotation section that by means of rotation causes the magnetism suppressing element to come to the masking position and a withdrawal position withdrawn from the masking position.
According to the present invention, a small fixing apparatus can be provided that can prevent an excessive rise in temperature of a paper non-passage area due to diverted flow of magnetic flux from a paper passage area of a heat-producing element to a paper non-passage area.
Embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the drawings, configuration elements and equivalent parts that have identical configurations or function are assigned the same codes, and descriptions thereof are not repeated.
As shown in
In
Laser beam scanner 103 outputs a laser beam 104 modulated in accordance with a time series electrical digital pixel signal of image information input from a host apparatus such as an image reading apparatus or computer (not shown), and performs scanning exposure of the surface of uniformly charged photosensitive drum 101 with laser beam 104. By this means, the absolute value of the potential of exposed parts of photosensitive drum 101 falls and becomes a light potential VL, and an electrostatic latent image is formed on the surface of photosensitive drum 101.
Developing unit 105 is provided with a rotated developing roller 106. Developing roller 106 is positioned opposite photosensitive drum 101, and a thin layer of toner is formed on its peripheral surface. A developing bias voltage with an absolute value smaller than dark potential V0 of photosensitive drum 101 and larger than light potential VL is applied to developing roller 106.
By this means, negatively charged toner on developing roller 106 adheres only to light potential VL parts of the surface of photosensitive drum 101, the electrostatic latent image formed on the surface of photosensitive drum 101 is developed, and an unfixed toner image 111 is formed on photosensitive drum 101.
Meanwhile, paper feed apparatus 107 feeds recording paper 109 as a recording medium one sheet at a time at predetermined timing by means of a paper feed roller 108. Recording paper 109 fed from paper feed apparatus 107 is transported through a pair of registration rollers 110 to the nip area between photosensitive drum 101 and a transfer roller 112 at appropriate timing synchronized with the rotation of photosensitive drum 101. By this means, unfixed toner image 111 on photosensitive drum 101 is transferred to recording paper 109 by transfer roller 112 to which a transfer bias is applied.
Recording paper 109 on which unfixed toner image 111 is formed and held in this way is guided by a recording paper guide 114 and separated from photosensitive drum 101, and then transported toward the fixing area of fixing apparatus 200. Once transported to this fixing area, recording paper 109 has unfixed toner image 111 heat-fixed onto it by fixing apparatus 200.
After passing through fixing apparatus 200, recording paper 109 onto which unfixed toner image 111 has been heat-fixed is ejected onto an output tray 116 attached to the outside of image forming apparatus 100.
After recording paper 109 has been separated from it, photosensitive drum 101 has residual material such as untransferred toner remaining on its surface removed by a cleaning apparatus 113, and is made ready for the next image forming operation.
The fixing apparatus of image forming apparatus 100 shown in
In
Rocking plate 203 rocks in a clockwise direction about short shaft 202 through the contracting action of a coil spring 204. Fixing roller 240 is displaced in line with this rocking of rocking plate 203, and through this displacement presses against pressure roller 250 with fixing belt 210 between. Supporting roller 220 is energized in the opposite direction to fixing roller 240 by a spring (not shown), by which means predetermined tension is imparted to fixing belt 210.
Pressure roller 250 is rotated in the direction indicated by the arrow by a driving source (not shown). Fixing roller 240 is rotated driven by the rotation of pressure roller 250 while gripping fixing belt 210. By this means, fixing belt 210 is rotated in the direction indicated by the arrow, gripped between fixing roller 240 and pressure roller 250. By means of this gripping and rotation of fixing belt 210, a nip area for heat-fixing unfixed toner image 111 onto recording paper 109 is formed between fixing belt 210 and pressure roller 250.
Excitation apparatus 230 comprises an IH type induction heating section, and as shown in
Exciting coil 231 is formed using litz wire comprising bundled thin wires, and the cross-sectional shape is formed as a semicircle so as to cover the outer peripheral surface of fixing belt 210 suspended on supporting roller 220. An excitation current with a drive frequency of 25 kHz is applied to exciting coil 231 from an exciting circuit (not shown). By this means, an alternating field is generated between core 232 and opposed core 233, an eddy current is generated in the conductive layer of fixing belt 210, and fixing belt 210 produces heat. In this example, the configuration is such that fixing belt 210 produces heat, but a configuration may also be used whereby supporting roller 220 is made to produce heat, and heat from supporting roller 220 is transferred to fixing belt 210.
Core 232 is attached to the center and part of the rear of exciting coil 231. As an alternative to ferrite, a high-permeability material such as permalloy can also be used as the material of core 232 and opposed core 233.
In fixing apparatus 200, as shown in
A temperature sensor 260 comprising a thermistor is positioned on the part of the rear surface of fixing belt 210 that has passed the area of contact with supporting roller 220. The temperature of fixing belt 210 is detected by this temperature sensor 260. The output of temperature sensor 260 is provided to a control apparatus (not shown). Based on the output of temperature sensor 260, this control apparatus controls the power supplied to exciting coil 231 via the exciting circuit so that an optimal image fixing temperature is attained, and by this means the calorific value of fixing belt 210 is controlled.
Downstream in the recording paper 109 transportation direction, an ejection guide 270 that guides recording paper 109 toward output tray 116 after heat-fixing is finished is provided in the area where fixing belt 210 is suspended on fixing roller 240.
A coil guide 234 serving as a supporting member is also provided in excitation apparatus 230, integral with exciting coil 231 and core 232. This coil guide 234 is formed of a resin with a high heat-resistance temperature such as a PEEK material or PPS. The provision of coil guide 234 makes it possible to confine heat emitted from fixing belt 210 in the space between fixing belt 210 and exciting coil 231, and prevent damage to exciting coil 231.
Although core 232 shown in
Fixing belt 210 comprises, for example, a thin endless belt with a diameter of 50 mm and thickness of 50 μm, with a conductive layer formed by dispersing silver powder in base material of polyimide resin with a glass transition point of 360 (° C.). The conductive layer may be composed of 2 or 3 laminated silver layers with a thickness of 10 μm. The surface of this fixing belt 210 may be coated with a 5 μm thick release layer of fluororesin (not shown) to provide releasability. It is desirable for the glass transition point of the material of fixing belt 210 to be in a range from 200 (° C.) to 500 (° C.). Resin or rubber with good releasability such as PTFE, PFA, FEP, silicone rubber, fluororubber, or the like, may be used, alone or mixed, for the release layer on the surface of fixing belt 210.
As an alternative to the above-mentioned polyimide resin, a heat-resistant resin such as fluororesin or metal such as an electroformed thin nickel sheet or thin stainless sheet can also be used as the base material of fixing belt 210. For example, fixing belt 210 may be configured by executing 10 μm thick copper plating on a 40 μm thick SUS304 (magnetic) or SUS304(nonmagnetic) surface.
When fixing belt 210 is used as an image heating element for heat-fixing of monochrome images, it is sufficient to secure releasability, but when fixing belt 210 is used as an image heating element for heat-fixing of color images, it is desirable for elasticity to be provided by forming a thick rubber layer. The heat capacity of fixing belt 210 should preferably be 60 J/K or less, and still more preferably 40 J/K or less.
Supporting roller 220 is a cylindrical metal roller 20 mm in diameter, 320 mm in length, and 0.2 mm thick. It is desirable for a magnetic metal such as iron or nickel to be used as the material of supporting roller 220.
When opposed core 233 opposite exciting coil 231 is used as shown in
Fixing roller 240 is 30 mm in diameter and made of silicone rubber, an elastic foam material with low surface hardness (here, JISA 30 degrees) and low thermal conductivity.
Pressure roller 250 is made of silicone rubber with a hardness of JISA 65 degrees. A heat-resistant resin or other rubber such as fluororubber or fluororesin may also be used as the material of pressure roller 250. It is also desirable for the surface of pressure roller 250 to be coated with resin or rubber such as PFA, PTFE, or FEP, alone or mixed, to increase wear resistance and releasability. Furthermore, it is desirable for pressure roller 250 to be made of a material with low thermal conductivity.
The configuration of a fixing apparatus according to Embodiment 1 will now be described in greater detail.
In
For cutaway parts 333a and 333b the center core 333 forming position is decided according to the paper passage reference of recording paper 109. Here, cutaway parts 333a and 333b are formed at both ends of center core 333 taking the paper passage reference of recording paper 109 as the center reference.
The length of center core 333 is formed so as to exceed the width of B4 size recording paper, which is the maximum paper passage area width of heat-producing roller 310. Here, as shown in
In
Here, as shown in
Similarly, when cutaway parts 333a are rotated from their withdrawal position to their masking position by rotation section 500, magnetic coupling between center core 333 and heat-producing roller 310 corresponding to paper non-passage areas of heat-producing roller 310 when A4 size recording paper is passed through is suppressed by cutaway parts 333a.
In this way., this fixing apparatus 300 controls magnetic coupling between center core 333 and heat-producing roller 310 by rotating cutaway parts 333a and 333b from their withdrawal position to their masking position by means of rotation section 500.
That is to say, in this fixing apparatus 300, through the rotation of center core 333, the distance between heat-producing roller 310 and center core 333 in areas corresponding to the paper non-passage areas varies according to whether cutaway parts 333a and 333b constituting magnetism suppressing elements have been moved to the masking position shown in
The distance between heat-producing roller 310 and center core 333 in areas corresponding to paper non-passage areas is increased when cutaway parts 333a or 333b have been moved to the masking position, as shown in
Also, magnetic coupling between center core 333 and heat-producing roller 310 strengthens when the distance between center core 333 and heat-producing roller 310 decreases, and weakens when the distance between center core 333 and heat-producing roller 310 increases.
Therefore, with this fixing apparatus 300, an excessive rise in temperature of paper non-passage areas of heat-producing roller 310 can be suppressed by weakening the magnetic coupling between center core 333 and heat-producing roller 310 by moving cutaway parts 333a and 333b to the masking position by rotating center core 333 by means of rotation section 500.
Also, in this fixing apparatus 300, since switching of the intensity of magnetic coupling between center core 333 and heat-producing roller 310 can be performed simply by rotating center core 333, the paper passage area width of heat-producing roller 310 can easily be made to accommodate the paper widths of two sizes of recording paper—A4 size and B4 size—as shown in
Furthermore, with this fixing apparatus 300, since the magnetism suppressing elements are configured as cutaway parts 333a and 333b formed in center core 333, it is not necessary for the magnetism suppressing elements to be provided as separate members, enabling the configuration to be made simpler and less expensive.
Next, the configuration of distinctive parts of a fixing apparatus according to Embodiment 2 will be described.
Magnetism masking members 701a and 701b serving as magnetism suppressing elements are formed of a material that can mask magnetic coupling between center core 333 and heat-producing roller 310 corresponding to paper non-passage areas of heat-producing roller 310—for example, an inexpensive, low-permeability electrical conductor such as copper or aluminum. As shown in
As with fixing apparatus 300 according to Embodiment 1, fixing apparatus 700 according to Embodiment 2 has the paper passage reference of recording paper 109 as a center reference, and magnetism masking members 701a and 701b are formed at both ends of center core 333.
Here, center core 333 is formed so as to exceed the width of B4 size recording paper, which is the maximum paper passage area width of heat-producing roller 310. Here, as shown in
Magnetism masking members 701a and 701b are rotated together with center core 333 by means of a rotation section 900 shown in
In
Here, as shown in
Similarly, when magnetism masking members 701a are rotated from their withdrawal position to their masking position by rotation section 900, magnetic coupling between center core 333 and heat-producing roller 310 corresponding to paper non-passage areas of heat-producing roller 310 when A4 size recording paper is passed through is suppressed by magnetism masking members 701a.
In this way, this fixing apparatus 700 blocks or boosts magnetic coupling between center core 333 and heat-producing roller 310 by rotating magnetism masking members 701a and 701b from their withdrawal position to their masking position by means of rotation section 900.
That is to say, in this fixing apparatus 700, when magnetism masking members 701a and 701b have been moved to the masking position shown in
Thus, with this fixing apparatus 700, an excessive rise in temperature of paper non-passage areas of heat-producing roller 310 can be suppressed by having the magnetic coupling between center core 333 and heat-producing roller 310 blocked by moving magnetism masking members 701a and 701b to the masking position by rotating center core 333 by means of rotation section 900.
Also, in this fixing apparatus 700, as with fixing apparatus 300 according to Embodiment 1, since the magnetic coupling between center core 333 and heat-producing roller 310 can be blocked or boosted simply by rotating center core 333, the paper passage area width of heat-producing roller 310 can easily be made to accommodate the paper widths of two sizes of recording paper—A4 size and B4 size—as shown in
Furthermore, with this fixing apparatus 700, since the magnetism suppressing elements are configured as magnetism masking members 701a and 701b provided in center core 333, it is not necessary for the magnetism suppressing elements to be provided as separate members, enabling the configuration to be made simpler and less expensive.
Also, since this fixing apparatus 700 has a configuration whereby magnetism masking members 701a and 701b are positioned in the center of the windings of exciting coil 331, the necessity of making magnetism masking members 701a and 701b thin can be eliminated, and it is possible for their thickness to be increased to around 1 mm for example. As a result, the electrical resistance of magnetism masking members 701a and 701b becomes low, and heat production of magnetism masking members 701a and 701b is suppressed. Moreover, since magnetism masking elements 301 are provided in center core 333 composed of a material with high thermal conductivity and specific heat such as ferrite, heat generated by magnetism masking members 701a and 701b is conducted and dispersed in center core 333, and an excessive rise in temperature of magnetism masking members 701a and 701b is suppressed. Furthermore, increasing the thickness of magnetism masking members 701a and 701b reduces their electrical resistance, making it easier for an eddy current to flow. As a result, a repulsive field is strengthened, and magnetic flux can be more effectively masked. Also, since magnetism masking members 701a and 701b do not require through-holes 35, they can mask magnetic flux more effectively than magnetic flux masking shield 31 in
Next, the configuration of a fixing apparatus according to Embodiment 3 will be described.
In this fixing apparatus 1100, in addition to a magnetic flux path whose degree of magnetic coupling is regulated by magnetism masking members 701a and 701b serving as magnetism suppressing elements formed in center core 333, a new magnetic flux path is formed by bypass path section 332a of arch core 332.
Thus, in this fixing apparatus 1100 a new path can be secured by means of bypass path section 332a, making it possible to increase the number of paper passage area sizes for which paper passage is possible without causing an excessive rise in temperature of heat-producing roller 310.
That is to say, with this fixing apparatus 1100, within a closed-loop of magnetic path 600, an area in which magnetic flux between center core 333 and heat-producing roller 310 is concentrated is masked by magnetism masking members 701a and 701b. Therefore, in this fixing apparatus 1100, magnetic coupling between center core 333 and heat-producing roller 310 corresponding to paper non-passage areas of heat-producing roller 310 can be efficiently suppressed, the rotational-direction width of magnetism masking members 701a and 701b, which are above-described magnetism suppressing elements, can be made small, and, as shown in
Therefore, in this fixing apparatus 1100, it is possible to make the paper passage area of heat-producing roller 310 accommodate recording paper of two sizes regulated by the two magnetism masking members 701a and 701b formed in center core 333 and, as shown in
Also, since this fixing apparatus 1100 has a configuration whereby magnetism masking members 701a and 701b are positioned in the center of the windings of exciting coil 331, the necessity of making magnetism masking members 701a and 701b thin can be eliminated, and it is possible for their thickness to be increased to around 1 mm for example. As a result, the electrical resistance of magnetism masking members 701a and 701b becomes low, and heat production of magnetism masking members 701a and 701b is suppressed. Moreover, since magnetism masking elements 301 are provided in center core 333 composed of a material with high thermal conductivity and specific heat such as ferrite, heat generated by magnetism masking members 701a and 701b is conducted and dispersed in center core 333, and an excessive rise in temperature of magnetism masking members 701a and 701b is suppressed. Furthermore, increasing the thickness of magnetism masking members 701a and 701b reduces their electrical resistance, making it easier for an eddy current to flow. As a result, a repulsive field is strengthened, and magnetic flux can be more effectively masked. Also, since magnetism masking members 701a and 701b do not require through-holes 35, they can mask magnetic flux more effectively than magnetic flux masking shield 31 in
Next, the configuration of a fixing apparatus according to Embodiment 4 will be described.
The center core 1333 of this fixing apparatus 1300 is configured as a rectangular shaft. As shown in
That is to say, in this fixing apparatus 1300, through the rotation of center core 1333, the rotational-direction width of an opposite surface of center core 1333 facing paper non-passage areas of heat-producing roller 310 varies according to whether stepped parts 1333a and 1333b constituting magnetism suppressing elements have been moved to an opposing position opposite heat-producing roller 310 or have been moved to a withdrawal position in which they are withdrawn from heat-producing roller 310.
The rotational-direction width of an opposite surface of center core 1333 facing paper non-passage areas of heat-producing roller 310 is large width W1 when stepped parts 1333a and 1333b have been moved to the withdrawal position, and is narrow width W2 when stepped parts 1333a and 1333b have been moved to the opposing position. Also, magnetic coupling between heat-producing roller 310 and center core 1333 strengthens when the rotational-direction width of an opposite surface of center core 1333 facing paper non-passage areas of heat-producing roller 310 becomes greater, and weakens when the rotational-direction width of an opposite surface of center core 1333 facing paper non-passage areas of heat-producing roller 310 becomes narrower.
Therefore, according to this fixing apparatus 1300, an excessive rise in temperature of paper non-passage areas of heat-producing roller 310 can be suppressed by weakening the magnetic coupling between heat-producing roller 310 and center core 1333 and by moving stepped parts 1333a and 1333b to the opposing position by rotating center core 1333 by means of rotation section 500 (or 900).
Also, in this fixing apparatus 1300, since switching of the intensity of magnetic coupling between heat-producing roller 310 and center core 1333 can be performed simply by rotating center core 1333, the paper passage area width of heat-producing roller 310 can easily be made to accommodate paper widths of a plurality of sizes of recording paper.
Furthermore, with this fixing apparatus 1300, it is not necessary for the magnetism suppressing elements to be provided as separate members, enabling the configuration to be made simpler and less expensive. Thus, according to this fixing apparatus 1300, an excessive rise in temperature of paper non-passage areas of heat-producing roller 310 can easily be prevented when a plurality of sizes of recording paper are passed through.
Instead of the rectangular shape of center core 1333 in this fixing apparatus 1300 shown in
Also, a configuration may be used whereby magnetism masking members 1501a, 1501b, and 1501c of copper or aluminum are embedded in stepped parts of center core 1333.
Next, the configuration of a fixing apparatus according to Embodiment 5 will be described.
In this fixing apparatus 1600, endless belt 1602 is rotated by means of pulley 1601, and a part of center core 1633 corresponding to a paper non-passage area of heat-producing roller 310 is concealed by magnetism masking layer 1603 on the peripheral surface of this endless belt 1602 as shown in
By this means, the degree of magnetic coupling between center core 1633 and heat-producing roller 310 corresponding to a paper non-passage area concealed by magnetism masking layer 1603 of endless belt 1602, and an excessive rise in temperature of a paper non-passage area of heat-producing roller 310 is suppressed.
Also, in this fixing apparatus 1600, many magnetism masking layers 1603 serving as magnetism suppressing elements can be provided by making endless belt 1602 longer, enabling the heat-producing element to be configured so as to accommodate more paper-passage sizes (heating widths).
Next, the configuration of a fixing apparatus according to Embodiment 6 will be described.
As magnetism masking members 701b serving as magnetism suppressing elements block magnetic coupling between center core 333 and heat-producing roller 310, an excessive rise in temperature of paper non-passage areas of heat-producing roller 310 is suppressed. However, a little leakage flux is generated that reaches heat-producing roller 310 from arch core 332 via exciting coil 331. As this leakage flux is blocked by leakage magnetism masking element 1801, an excessive rise in temperature of paper non-passage areas is effectively suppressed.
It is desirable for leakage magnetism masking element 1801 to be narrower than the width of the winding section of exciting coil 331. In this way, when the maximum paper passage area width of heat-producing roller 310 is heated, leakage magnetism masking element 1801 does not affect the closed loop of magnetic path 600 shown in
In the fixing apparatuses according to the above-described embodiments, heat-producing roller 310 has been used as the heat-producing element, but this heat-producing element may also be fixing belt 210 shown in
In the fixing apparatuses according to the above-described embodiments, the magnetic path forming element in which magnetism suppressing elements are provided is assumed to be center core 333 (or 1333), but the magnetic path forming elements that provide the magnetism suppressing elements may also be side cores 334 provided at the sides of exciting coil 331 that transect the magnetic path of arch core 332. According to this configuration, switching can be performed of the intensity of magnetic coupling between side cores 334 and heat-producing roller 310 corresponding to paper non-passage areas of heat-producing roller 310.
The fixing apparatuses according to the above-described embodiments are configured with exciting coil 331 serving as a magnetic flux generation section, center core 333, and so forth located outside heat-producing roller 310. A fixing apparatus with this kind of configuration allows ample space for installing center core 333 serving as the magnetic path forming element and its rotation section 500, and offers improved freedom of design for the body of the apparatus. Also, since a fixing apparatus with this configuration has magnetism masking members 701a and 701b located outside heat-producing roller 310, heat generated in magnetism masking members 701a and 701b is more readily dissipated by natural convection of the surrounding air. Moreover, forced circulation cooling by means of a fan can also be performed easily.
In the fixing apparatuses according to the above-described embodiments, since exciting coil 331 serving as a magnetic flux generation section, center core 333, and so forth are located outside heat-producing roller 310, working efficiency is good for the replacement or maintenance of parts such as consumable heat-producing roller 310.
The present application is based on Japanese Patent Application No. 2003-358023, filed on Oct. 17, 2003, the entire content of which is expressly incorporated herein by reference.
As described above, a fixing apparatus of the present invention can be configured compactly and can prevent an excessive rise in temperature of a paper non-passage area due to diverted flow of magnetic flux from a paper passage area of a heat-producing element to a paper non-passage area, and is therefore useful as a fixing apparatus of an electrophotographic or electrostatographic copier, facsimile machine, printer, or the like.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2003-358023 | Oct 2003 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2004/014753 | 10/6/2004 | WO | 00 | 4/11/2006 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2005/038535 | 4/28/2005 | WO | A |
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