JP2006195322A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize high heating efficiency and a long life time, to shorten time need for a temperature rise and to reduce consumption power, in a fixing device that heats a fixing roller by the contact of a heated belt with the fixing roller. <P>SOLUTION: The fixing device 1 includes a fixing section 10 and a heating section 20. The heating section 20 has the belt 21 and a magnetic flux generating means 50. The belt 21 is endless shape, has a magnetic metal layer 24 as a heat generating layer, and is disposed so that part of it is in contact with the fixing roller 11. The magnetic flux generating means 50 is disposed near the area of the contact of the belt 21 and fixing roller 11 and inside the belt 21. The magnetic flux generating means 50 has excitation coils 51 and a ferrite 53, or a highly magnetically permeable member, for intensifying a magnetic field. A magnetic filed is generated by causing a high frequency current to flow in the excitation coils 51 of the magnetic flux generating means 50. When the thus generated magnetic flux M is passed through the magnetic metal layer 24 of the belt 21, an eddy current flows in the metal of the passage area A. Subsequently, heat is generated by the electric resistance of the metal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fixing device that inserts a sheet carrying an unfixed toner image into the nip of a heated roller pair, heats and melts the unfixed toner, and fixes the sheet on the sheet.

  In an electrophotographic image forming apparatus, a heat source is incorporated in at least one roller of a roller pair forming a nip, and a sheet carrying an unfixed toner image is inserted into the nip of the roller pair heated by the heat source. Thus, a heat roller fixing method for fixing toner onto a sheet is widely used.

However, the heat roller fixing method has problems such as a decrease in the surface temperature of the fixing roller, which is a heat roller, or an increase in the temperature rising time until the fixing roller surface reaches a fixable temperature. There was concern. Therefore, in order to solve such problems, the fixing roller heating method has been devised, the temperature of the fixing roller surface is prevented from lowering, the time required for raising the temperature to a predetermined temperature is shortened, and the surface temperature is maintained. A possible fixing device has been proposed, and an example of the fixing device can be seen in Japanese Patent Application Laid-Open No. H10-228707.
JP 2004-54225 A (page 8-13, FIG. 2)

  In the fixing device described in Patent Document 1, an endless belt provided with heating means inside is brought into contact with the fixing roller, and the surface of the fixing roller is heated by this belt. However, since a heat source capable of radiating heat, such as a halogen lamp, is used as a heating means, and the direction of heat radiation from the heat source cannot be limited, only the contact portion between the belt and the fixing roller is locally heated. I can't. Accordingly, since the heating efficiency is poor, the power consumption is large, and a great effect cannot be obtained for shortening the time until the fixing roller surface reaches a fixing temperature. In addition, when a sheet heating element using a resistance heating element made of a ceramic heater or the like is used as another heating means, high heating efficiency can be obtained because the sheet heating element is directly heated by contacting the belt. There is a high possibility of causing problems such as a decrease in the belt life due to the belt and poor rotation of the belt.

  The present invention has been made in view of the above points, and in a fixing device that heats the surface of a heated endless belt in contact with a fixing roller, high heating efficiency can be achieved without bringing a heat source into contact with the belt. An object of the present invention is to provide a fixing device that proposes a structure to be obtained, has a long service life, and can shorten the temperature rise time and power consumption.

  In order to solve the above-described problems, the present invention includes a fixing roller, a plurality of belt support rollers, an endless belt that is wound around the belt support rollers and a part of which is in contact with the fixing roller. A fixing roller for fixing an unfixed toner image carried on the paper at the nip portion, wherein the belt is formed of a magnetic metal. A layer is provided, and magnetic flux generating means is arranged inside the belt.

  Further, the magnetic flux generating means is arranged so that the magnetic flux is generated at a contact portion between the belt and the fixing roller.

  Further, the magnetic flux generating means includes a highly permeable member.

  Further, magnetic flux adjusting means for adjusting the density of the magnetic flux passing through the belt is provided.

  Further, the magnetic flux adjusting means displaces the position of the magnetic flux generating means or the high magnetic permeability member in the axial direction of the fixing roller.

  Further, the magnetic flux adjusting means displaces the position of the magnetic flux generating means or the highly permeable member in a direction approaching / separating from the belt.

  The highly permeable member is ferrite.

  The plurality of belt support rollers are made of a nonmagnetic material or a high specific resistance material.

  According to the configuration of the present invention, in the fixing device including the endless belt that contacts the fixing roller, the belt includes the magnetic metal layer, and the magnetic flux generation means is disposed inside the belt. The belt can be heated directly by the induced current generated by the generating means. Thereby, heat does not move in the air from the heat source, high heating efficiency can be obtained, heating time can be shortened, and power consumption can be reduced. Further, since the belt can be directly heated at any time, it is possible to quickly cope with a temperature drop on the surface of the fixing roller. Thereby, the temperature fluctuation of the fixing roller surface can be reduced, and the fixing roller surface can be easily held at a suitable temperature. Further, since the magnetic flux generating means is not in contact with the belt, the belt does not wear or cause rotation failure. With such a structure, it is possible to obtain a fixing device that can extend the life, shorten the temperature raising time, and reduce power consumption.

  Further, since the magnetic flux generating means is arranged so that the magnetic flux is generated at the contact portion between the belt and the fixing roller, the energy generated by the magnetic flux generating means in the belt is sufficiently transmitted to the fixing roller. be able to. Therefore, it is possible to further improve the performance related to the heating efficiency and the power consumption, and to obtain a stable fixing property.

  In addition, since the magnetic flux generation means includes the high magnetic permeability member, most of the magnetic flux generated from the magnetic flux generation means passes through the high magnetic permeability member, and the magnetic field can be strengthened. Therefore, the inductance can be improved by the high magnetic permeability member, and the magnetic flux generating means can be downsized.

  Since the magnetic flux adjusting means for adjusting the density of the magnetic flux passing through the belt is provided, the heating range of the belt can be set to a range corresponding to the paper size. Here, in many normal fixing devices, the sheet passes through the central portion of the fixing roller. The paper is rarely the maximum width paper that can be passed, and in most cases it is a paper with a shorter width. As a result, the central portion of the fixing roller is more easily deprived of heat by the passing paper than the both ends. So, according to the said structure, heat can be collected in the center part which is easy to lose heat. Therefore, it is possible to heat only the necessary range of the belt, and it is possible to further suppress the occurrence of temperature unevenness and further improve the performance relating to the heating efficiency and power consumption.

  Further, since the magnetic flux adjusting means displaces the position of the magnetic flux generating means or the highly permeable member in the axial direction of the fixing roller, for example, the paper width is narrow and one of the fixing roller in the axial direction is fixed. When the paper is brought close to the end portion, the magnetic flux generating means and the high magnetic permeability member can be moved to a place where the paper passes. As a result, it is possible to perform heating control according to the paper width, prevent waste of heating energy, and obtain high heating efficiency.

  Further, since the magnetic flux adjusting means displaces the position of the magnetic flux generating means or the high magnetic permeability member in a direction approaching / separating from the belt, the magnetic flux generating means or the high magnetic permeability member is moved. When the paper width is narrow, the magnetic flux density is increased close to the belt, and when the paper width is wide, the magnetic flux density is decreased away from the belt. As a result, when the paper width is narrow, the central portion in the axial direction of the belt generates heat, and when the paper width is wide, heat is generated over almost the entire belt. In this way, it is possible to perform heating control according to the paper width, prevent waste of heating energy, and improve heating efficiency.

  In addition, since the high magnetic permeability member is ferrite, it is possible to employ the ferrite widely used as the high magnetic permeability member and increase the heating efficiency with a simpler configuration.

  Further, since the plurality of belt support rollers are made of a non-magnetic material or a high specific resistance material, it is possible to suppress the generation of an induced current inside the belt support roller. As a result, the belt support roller does not generate heat, and energy obtained by the magnetic flux generation means is not taken away by the belt support roller. Therefore, the heating efficiency of the belt by the magnetic flux generating means can be further improved.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  First, the configuration of the fixing device according to the first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic vertical sectional front view of a fixing device, FIG. 2 is a schematic enlarged front view of a belt, and FIG. 3 is a schematic perspective view of magnetic flux generating means.

  As shown in FIG. 1, the fixing device 1 includes a fixing unit 10, a heating unit 20, and a pressure unit 30. A paper entry guide 40 is provided at a location where the paper enters toward the fixing device 1.

  The fixing unit 10 includes a fixing roller 11. The fixing roller 11 has a diameter of 40 mm, and an elastic member layer 13 made of silicon rubber or sponge is provided outside a cored bar 12 made of metal such as stainless steel. A release layer 14 having a thickness of 50 μm is provided outside the elastic member layer 13 and on the surface of the fixing roller 11 to enhance the toner releasability. The release layer 14 is made of a fluorine-based resin such as PFA (tetrafluoroethylene-per-fluoroalkyl vinyl ether copolymer) and is provided by covering with a coating or a tube by spraying. The fixing roller 11 is rotated by a driving device (not shown) so that the peripheral speed thereof is the same as the paper conveyance speed.

  A thermistor 15 is provided outside the fixing roller 11. The thermistor 15 detects the temperature of the surface of the fixing roller 11 and controls the temperature by controlling the output of a high-frequency power source 54 of a magnetic flux generating means 50 described later.

  The heating unit 20 is disposed at a position facing the pressure unit 30 with the fixing roller 11 of the fixing unit 10 interposed therebetween. The heating unit 20 includes a belt 21, a plurality of belt support rollers 22, and magnetic flux generation means 50.

  The belt 21 is an endless belt as shown in FIG. 1, and its width is substantially the same as the width of the fixing roller 11. In the belt 21, a magnetic metal layer 24 made of a ferromagnetic conductive material such as nickel is provided on the polyimide film 23 shown in FIG. 2 by plating or rolling. A PFA tube having a thickness of 50 μm is covered as a release layer 25 on the outside of the magnetic metal layer 24. The belt 21 is wound around three belt support rollers 22 and given a predetermined tension. Each of the belt support rollers 22 is made of a non-magnetic metal such as aluminum that hardly generates an induced current, or a high specific resistance material such as a synthetic resin. The belt 21 does not have a driving device and is rotated according to the rotation of the fixing roller 11.

  Such a belt 21 is arranged so as to be in pressure contact with the fixing roller 11 at an intermediate portion between the two belt support rollers 22. Due to the pressure contact of the belt 21 to the fixing roller 11, this portion of the belt 21 is concave toward the inside of the belt 21. Accordingly, when the fixing roller 11 rotates, the belt 21 rotates so as to move along the peripheral surface of the fixing roller 11 at the contact point with the fixing roller 11.

  As shown in FIGS. 1 and 3, the magnetic flux generation means 50 is disposed inside the belt 21 and in the vicinity of the contact portion between the belt 21 and the fixing roller 11 with a gap. Yes. The magnetic flux generation means 50 extends in the axial direction of the fixing roller 11, that is, in the paper width direction, and has substantially the same width as the width of the fixing roller 11. The magnetic flux generating means 50 includes an exciting coil 51, a support member 52, and a ferrite 53 that is a highly permeable member.

  The exciting coil 51 is obtained by winding a litz wire obtained by bringing 300 enamel wires having a diameter of 0.1 mm close to each other along the axis of the fixing roller 11. The support member 52 is made of a heat resistant resin, and a bottom portion thereof is curved toward the belt 21 in accordance with the shape of the belt 21. A ferrite storage portion 52 a extending in the axial direction of the fixing roller 11 is provided at the center portion of the support member 52. The exciting coil 51 is wound so as to surround the ferrite storage portion 52a. Ferrite 53, which is a highly permeable member for increasing the magnetic field, is provided inside and outside the exciting coil 51 wound in this way. The ferrite 53 has an E shape when viewed from the axial direction of the fixing roller 11 and is divided into a plurality of pieces in the axial direction of the fixing roller 11. The ferrite 53 is provided so as to cover the support member 52 from above. A high frequency power supply 54 with a rated power of 1500 W and a frequency of 20 to 50 kHz is connected to the excitation coil 51.

  The litz wire constituting the exciting coil 51 may be wound in a direction along the circumference of the fixing roller 11. Moreover, as long as the ferrite 53 is a member having high magnetic permeability, it can be replaced with a member other than ferrite, and may be singular. The magnetic flux generation means 50 may be configured not to have a highly permeable member such as the ferrite 53.

  The pressure unit 30 includes a pressure roller 31. Similar to the fixing roller 11, the pressure roller 31 has a diameter of 40 mm, and an elastic member layer 33 made of silicon rubber or sponge is provided outside a cored bar 32 made of a metal such as stainless steel. The pressure roller 31 is in contact with the fixing roller 11 to form a nip portion through which the sheet is inserted. The pressure roller 31 does not have a driving device and is rotated according to the rotation of the fixing roller 11 by contacting the fixing roller 11.

  Next, the heating operation of the fixing device 1 will be described with reference to FIG. FIG. 4 is a schematic vertical sectional front view showing the fixing device in a heated state.

  When a high frequency current is passed through the exciting coil 51 of the magnetic flux generating means 50, a magnetic field is generated. Since most of the generated magnetic flux M passes through the ferrite 53, which is a highly permeable member, the magnetic field can be strengthened. When the generated magnetic flux M passes through the magnetic metal layer 24 of the belt 21, an eddy current flows through the metal in the passing area A that is a contact portion with the fixing roller 11, and heat is generated by the electric resistance of the metal. Since the fixing roller 11 is in contact with the belt 21 in a wide range of the region A, the heat of the belt 21 is easily transmitted to the surface of the fixing roller 11.

  Thus, in the fixing device 1 including the endless belt 21 that contacts the fixing roller 11, the belt 21 includes the magnetic metal layer 24, and the magnetic flux generation means 50 is disposed inside the belt 21. The belt 21 can be directly heated by the induced current generated by the magnetic flux generation means 50. Thereby, heat does not move in the air from the heat source, high heating efficiency can be obtained, heating time can be shortened, and power consumption can be reduced. Further, since the belt 21 can be directly heated at any time, it is possible to quickly cope with a temperature drop on the surface of the fixing roller 11. Thereby, the temperature fluctuation on the surface of the fixing roller 11 can be reduced, and the surface of the fixing roller 11 can be easily held at a suitable temperature. Further, since the magnetic flux generating means 50 is not in contact with the belt 21, the belt is not worn or does not cause rotation failure. With such a structure, it is possible to obtain the fixing device 1 that can extend the life, shorten the temperature raising time, and reduce the power consumption.

  Further, since the magnetic flux generating means 50 is arranged so that the magnetic flux is generated at the contact point between the belt 21 and the fixing roller 11, the energy generated by the magnetic flux generating means 50 on the belt 21 is sufficiently increased. Can tell. Therefore, it is possible to further improve the performance related to the heating efficiency and the power consumption, and to obtain a stable fixing property.

  Furthermore, since the magnetic flux generation means 50 includes a highly permeable member, most of the magnetic flux generated from the magnetic flux generation means 50 passes through the highly permeable member, and the magnetic field can be strengthened. Therefore, the inductance can be improved by the high magnetic permeability member, and the magnetic flux generating means 50 can be downsized.

  In addition, since the highly permeable member is the ferrite 53, the ferrite 53 widely used as the highly permeable member is employed, and the heating efficiency can be increased with a simpler configuration.

  Since the plurality of belt support rollers 22 are made of a non-magnetic material such as aluminum or a high specific resistance material such as synthetic resin, it is possible to suppress the generation of induced current in the belt support roller 22. As a result, the belt support roller 22 does not generate heat and the belt support roller 22 does not lose energy obtained by the magnetic flux generation means 50. Therefore, the heating efficiency of the belt 21 by the magnetic flux generation means 50 can be further improved.

  Next, a fixing device 1 according to a second embodiment of the present invention will be described with reference to FIGS. 5 and 6. FIG. 5 is a schematic perspective view of the magnetic flux generating means of the fixing device, and FIG. 6 is a schematic vertical sectional side view of the belt and the magnetic flux generating means as seen from the sheet conveying direction, and a graph showing the heat generation amount of the belt. Since the basic configuration of this embodiment is the same as that of the first embodiment shown in FIGS. 1 to 4, the description of the drawings and the description of components common to the first embodiment are omitted. Shall be omitted.

  In the fixing device 1 according to the second embodiment, the ferrite 53 of the magnetic flux generator 50 is shorter than the width of the support member 52 and the exciting coil 51 and is about ½ as shown in FIG. The ferrite 53 can be displaced in the direction of the white arrow in FIG. 5, that is, in the axial direction of the fixing roller 11.

  The moving mechanism of the ferrite 53 is a magnetic flux adjusting means (not shown). The magnetic flux adjusting means adjusts the density of the magnetic flux passing through the belt 21 by displacing the ferrite 53 in the axial direction of the fixing roller 11. As a result, when the sheet passes through the central portion in the axial direction of the fixing roller 11, as shown in FIG. 6, the ferrite 53 is arranged in the central portion (the chain line in the drawing), and the region A1 of the belt 21 is mainly heated. The central portion of the fixing roller 11 is heated. Further, when the sheet passes through one end portion of the fixing roller 11, the ferrite 53 is moved to the end portion, and the region A2 of the belt 21 is mainly heated so that one side of the fixing roller 11 is heated.

  Thus, since the magnetic flux adjusting means for adjusting the density of the magnetic flux passing through the belt 21 is provided, the heating range of the belt 21 can be set to a range corresponding to the paper size. Therefore, it is possible to heat only the necessary range of the belt 21, and it is possible to further suppress the occurrence of temperature unevenness and further improve the performance related to heating efficiency and power consumption.

  Further, since the magnetic flux adjusting means displaces the position of the ferrite 53 which is a highly permeable member in the axial direction of the fixing roller 11, for example, the paper width is narrow, and the paper is placed at one end in the axial direction of the fixing roller 11. When passing the paper, it is possible to move the ferrite 53 to a place where the paper passes. As a result, it is possible to perform heating control according to the paper width, prevent waste of heating energy, and obtain high heating efficiency.

  In many ordinary fixing devices 1, the sheet passes through the central portion of the fixing roller 11. The paper is rarely the maximum width paper that can be passed, and in most cases it is a paper with a shorter width. Thereby, the central portion of the fixing roller 11 is more easily deprived of heat by the passing paper than the both ends. So, according to the said structure, heat can be collected in the center part which is easy to lose heat.

  Note that the magnetic flux adjusting means in this embodiment may be one that displaces not only the ferrite 53 that is a highly permeable member but also the entire magnetic flux generating means 50 in the axial direction of the fixing roller 11.

  Next, a fixing device 1 according to a third embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a schematic vertical sectional front view of the fixing device, and FIG. 8 is a schematic vertical sectional side view of the belt and magnetic flux generating means viewed from the sheet conveying direction, and a graph showing the heat generation amount of the belt. Since the basic configuration of this embodiment is the same as that of the first and second embodiments, the description of the drawings and the description of components common to these embodiments will be omitted. To do.

  In the fixing device 1 according to the third embodiment, the magnetic flux generation means 50 can be displaced in the direction of the white arrow in FIG. 7, that is, in the direction approaching / separating from the belt 21. The moving mechanism of the magnetic flux generating means 50 is a magnetic flux adjusting means (not shown). The magnetic flux adjusting means passes the belt 21 by displacing the magnetic flux generating means 50 in a direction approaching / separating from the belt 21. Adjust the magnetic flux density. As a result, when the paper width is narrow, as shown in FIG. 8, the magnetic flux generating means 50 is brought close to the belt 21 (one-dot chain line in the figure), and the area A1 of the belt 21 is mainly heated to center the fixing roller 11 in the axial direction. Heat the part. Further, when the paper width is wide, the magnetic flux generating means 50 is separated from the belt 21, and the area A <b> 2 of the belt 21 is heated to generate heat over almost the entire area of the fixing roller 11 in the axial direction.

  In this way, the magnetic flux adjusting means displaces the position of the magnetic flux generating means 50 in the direction approaching / separating from the belt 21, so that the magnetic flux generating means 50 is moved closer to the belt 21 when the paper width is narrow. When the paper width is wide, the density of the magnetic flux is reduced away from the belt 21. As a result, when the paper width is narrow, the central portion in the axial direction of the belt 21 generates heat, and when the paper width is wide, heat is generated over almost the entire area of the belt 21. Therefore, it is possible to perform heating control according to the sheet width, prevent waste of heating energy, and improve heating efficiency.

  Note that the magnetic flux adjusting means in this embodiment may be one that displaces not only the magnetic flux generating means 50 as a whole but only the ferrite 53, which is a highly permeable member, in a direction approaching / separating from the belt 21.

  Moreover, the numerical values such as dimensions that have appeared so far are exemplifications of preferred examples, and do not limit the scope of the invention.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  The present invention can be used in a fixing device in which a heated endless belt is brought into contact with a fixing roller to heat the surface thereof.

1 is a schematic vertical sectional front view of a fixing device according to a first embodiment of the present invention. FIG. 2 is a schematic partial enlarged front view of a belt of the fixing device shown in FIG. 1. It is a model perspective view of the magnetic flux generation means of the fixing device shown in FIG. FIG. 3 is a schematic vertical sectional front view showing the fixing device in a heated state. It is a model perspective view of the magnetic flux generation means of the fixing device according to the second embodiment of the present invention. 6 is a schematic vertical cross-sectional side view of a belt and magnetic flux generation means viewed from the paper conveyance direction of the second embodiment, and a graph showing the amount of heat generated by the belt. FIG. 6 is a schematic vertical sectional front view of a fixing device according to a third embodiment of the present invention. 10 is a schematic vertical cross-sectional side view of a belt and magnetic flux generation means viewed from the paper conveyance direction of the third embodiment, and a graph showing the amount of heat generated by the belt.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing device 10 Fixing part 11 Fixing roller 20 Heating part 21 Belt 22 Belt support roller 24 Magnetic metal layer (belt)
DESCRIPTION OF SYMBOLS 30 Pressure part 31 Pressure roller 50 Magnetic flux generation means 51 Excitation coil 52 Support member 53 Ferrite (highly magnetic permeability member)

Claims (8)

A fixing roller, a plurality of belt support rollers, an endless belt that is wound between the belt support rollers, a part of which is in contact with the fixing roller, and a sheet that is inserted into contact with the fixing roller A fixing device for fixing an unfixed toner image carried on a paper sheet at the nip portion, and a pressure roller that forms a nip portion;
The fixing device according to claim 1, wherein the belt includes a magnetic metal layer, and magnetic flux generation means is disposed inside the belt.   The fixing device according to claim 1, wherein the magnetic flux generation unit is arranged so that the magnetic flux is generated at a contact portion between the belt and the fixing roller.   The fixing device according to claim 1, wherein the magnetic flux generation unit includes a highly permeable member.   The fixing device according to claim 1, further comprising a magnetic flux adjusting unit that adjusts a density of a magnetic flux passing through the belt.   The fixing device according to claim 4, wherein the magnetic flux adjusting unit displaces the position of the magnetic flux generating unit or the high magnetic permeability member in an axial direction of the fixing roller.   6. The fixing according to claim 4, wherein the magnetic flux adjusting means displaces the position of the magnetic flux generating means or the highly permeable member in a direction approaching / separating from the belt. apparatus.   The fixing device according to claim 3, wherein the high magnetic permeability member is ferrite.   The fixing device according to claim 1, wherein the plurality of belt support rollers are made of a nonmagnetic material or a high specific resistance material.

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