JP2005352421A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable image forming apparatus where the malfunction of an electronic member caused by alternating magnetic field generated from an electromagnetic induction part is surely prevented. <P>SOLUTION: In the image forming apparatus equipped with the electromagnetic induction part to generate the alternating magnetic field in an image forming apparatus main body 1, a magnetic field shielding member 50 is provided at a part or all of the peripheries of the electronic members 39 and 41 provided in the image forming apparatus main body 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and more particularly to an image forming apparatus including a fixing unit using an electromagnetic induction heating method.

  Conventionally, in an image forming apparatus such as a copying machine or a printer, an apparatus using an electromagnetic induction heating type fixing unit is often used for the purpose of reducing energy consumption by reducing the rise time of the apparatus (for example, (See Patent Document 1).

  In Patent Document 1, etc., an electromagnetic induction heating type fixing unit (fixing device) includes a heating roller (heating roller), a fixing auxiliary roller (fixing roller), a fixing belt stretched between the heating roller and the fixing auxiliary roller, and heating. An electromagnetic induction unit (induction heating unit) that faces the roller via the fixing belt, a pressure roller that faces the fixing auxiliary roller via the fixing belt, and the like. The electromagnetic induction unit includes a coil unit extending in the width direction (a direction perpendicular to the conveyance direction of the recording medium), a core facing the coil unit, and the like.

The fixing belt is heated at a position facing the electromagnetic induction unit. The heated fixing belt heats and fixes the toner image on the recording medium conveyed to the positions of the auxiliary fixing roller and the pressure roller. Specifically, when a high frequency alternating current is passed through the coil portion, a magnetic field is formed around the coil portion, and an eddy current is generated on the surface of the heating roller. When an eddy current is generated in the heating roller, Joule heat is generated by the electric resistance of the heating roller itself. The fixing belt wound around the heating roller is heated by the Joule heat.
An image forming apparatus using such an electromagnetic induction heating type fixing unit is known as being capable of raising the surface temperature (fixing temperature) of a fixing belt to a desired temperature with a short start-up time with low energy consumption. ing.

  On the other hand, in Patent Document 2 and the like, an electronic component installed in a printer is provided with an electronic component in order to shield the electromagnetic wave incident on the electronic component from the outside and to prevent the electromagnetic wave from being emitted from the electronic component to the outside. A technique for covering with an electromagnetic wave shielding member is disclosed.

JP 2002-82549 A JP 2003-298283 A

  In the conventional image forming apparatus described above, the magnetic field formed by the electromagnetic induction unit may leak to the outside of the fixing unit, and the electronic member near the fixing unit may malfunction due to the leakage magnetic field. If electronic members such as the control unit, electronic board, power supply unit, sensor, and wiring malfunction, normal operation in the image forming apparatus is hindered.

  In particular, in recent downsized image forming apparatuses, since the interval between the constituent members is narrowed, the electronic members installed in the image forming apparatus main body are affected by the magnetic field leaking from the electromagnetic induction unit. It is easy. Therefore, the above-mentioned problem cannot be ignored.

  On the other hand, a measure to cover the periphery of the fixing unit with a magnetic field shielding member is conceivable so that the magnetic field generated by the electromagnetic induction unit does not leak outside the fixing unit. However, since the recording medium is carried in and out of the fixing unit, the fixing unit cannot be completely covered with the magnetic field shielding member. When an opening serving as a recording medium conveyance path is provided in the magnetic shielding member, a leakage magnetic field is generated from the opening. Electronic members such as a photo sensor that detects the toner density on the transfer belt and a photo sensor that detects jammed paper in the conveyance path are often installed near the conveyance path of the recording medium. Is likely to malfunction.

  Further, when the periphery of the fixing unit is covered with a magnetic field shielding member, the heat generated in the fixing unit is confined in the magnetic field shielding member, so that the magnetic field shielding member reaches a high temperature and the atmosphere in the image forming apparatus main body. The temperature will rise. In such a case, there is a possibility that the image forming process is affected, the constituent members of the apparatus main body are thermally damaged, or the electronic member malfunctions due to heat.

  On the other hand, in the above-mentioned Patent Document 2 and the like, by providing an electromagnetic wave shielding member made of aluminum around the electronic component, the electromagnetic wave incident on the electronic component from the outside is shielded and the emission of the electromagnetic wave from the electronic component to the outside is suppressed. ing. However, when this electromagnetic shielding member is installed around an electronic member of an image forming apparatus having an electromagnetic induction heating type fixing unit, an effect of shielding a leakage magnetic field and suppressing malfunction of the electronic member can hardly be expected. That is, since the magnetic field formed by the electromagnetic induction part is an alternating magnetic field, the magnetic field passes through aluminum which is a non-magnetic material.

  The present invention has been made to solve the above-described problems, and provides a highly reliable image forming apparatus in which malfunction of an electronic member due to an alternating magnetic field generated from an electromagnetic induction portion is reliably prevented. There is to do.

  An image forming apparatus according to a first aspect of the present invention is an image forming apparatus provided with an electromagnetic induction section for generating an alternating magnetic field in the image forming apparatus body, and an electronic member provided in the image forming apparatus body The magnetic field shielding member is provided in part or all of the periphery of the.

  An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the magnetic field shielding member is provided on a side facing the electromagnetic induction portion.

  An image forming apparatus according to a third aspect of the present invention is the image forming apparatus according to the first or second aspect, wherein the magnetic field shielding member has an opening.

  An image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to any one of the first to third aspects, wherein the magnetic field shielding member is formed of a metal material in a plate shape.

  An image forming apparatus according to a fifth aspect of the present invention is the image forming apparatus according to any one of the first to fourth aspects, wherein the magnetic field shielding member is formed of a metal material in a lattice shape.

  An image forming apparatus according to a sixth aspect of the present invention is the image forming apparatus according to the fourth or fifth aspect, wherein the metal material is permalloy or directional silicon steel.

  An image forming apparatus according to a seventh aspect of the present invention is the image forming apparatus according to any one of the first to sixth aspects, further comprising a cooling means for cooling the magnetic field shielding member.

  An image forming apparatus according to an eighth aspect of the present invention is the image forming apparatus according to the seventh aspect, wherein the cooling means is a heat radiating member installed on a surface of the magnetic field shielding member.

  An image forming apparatus according to a ninth aspect of the present invention is the image forming apparatus according to any one of the first to eighth aspects, wherein the electromagnetic induction portion is configured to heat the fixing member by electromagnetic induction. The fixing member heats the toner image and fixes the toner image on the recording medium.

  According to a tenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the fixing member is a fixing belt stretched between a heating roller and a fixing auxiliary roller, and the heating member The roller is disposed so as to face the electromagnetic induction portion facing the outer peripheral surface of the fixing belt via the fixing belt, and the auxiliary fixing roller presses the recording medium to be conveyed Is disposed so as to abut against the fixing belt via the fixing belt.

  An image forming apparatus according to an eleventh aspect of the present invention is the image forming apparatus according to the ninth aspect, wherein the fixing member is a fixing roller that comes into contact with a pressure roller for pressing a recording medium to be conveyed. The electromagnetic induction portion faces the outer peripheral surface or inner peripheral surface of the fixing roller.

  An image forming apparatus according to a twelfth aspect of the present invention is the image forming apparatus according to any one of the first to eleventh aspects, wherein the electronic member is controlled by the image forming apparatus main body. This is a control unit that performs the above.

  An image forming apparatus according to a thirteenth aspect of the present invention is the image forming apparatus according to any one of the first to twelfth aspects of the present invention, wherein the electronic member is supplied with electric power for image formation performed by the image forming apparatus main body. This is a power supply unit that supplies power.

  An image forming apparatus according to a fourteenth aspect of the present invention is the image forming apparatus according to any one of the first to thirteenth aspects, wherein the electronic member is an electronic substrate on which an electronic device is mounted. .

  An image forming apparatus according to a fifteenth aspect of the present invention is the image forming apparatus according to any one of the first to fourteenth aspects, wherein the electronic member is a wiring for energization.

  An image forming apparatus according to a sixteenth aspect of the present invention is the image forming apparatus according to any one of the first to fifteenth aspects, wherein the electronic member is a magnetic sensor installed in a developing section. .

  An image forming apparatus according to a seventeenth aspect of the present invention is the image forming apparatus according to any one of the first to sixteenth aspects, wherein the electronic member is a photosensor facing the image carrier. .

  The image forming apparatus according to claim 18 is the image forming apparatus according to claim 17, wherein the image carrier is at least one of a photoconductor, a transfer unit, an intermediate transfer unit, and a recording medium. It is.

  An image forming apparatus according to a nineteenth aspect of the present invention is the image forming apparatus according to any one of the first to eighteenth aspects, wherein the electronic member is installed in a transfer portion or an intermediate transfer portion. .

  The present invention provides a highly reliable image forming apparatus in which malfunction of an electronic member due to an alternating magnetic field generated from an electromagnetic induction portion is reliably prevented because a magnetic field shielding member is provided around the electronic member. can do.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
1 and 2, the first embodiment of the present invention will be described in detail.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, 1 is a main body of a laser printer as an image forming apparatus, 3 is an exposure unit that irradiates a photosensitive drum 18 with exposure light L based on image information, and 4 is detachably installed on the apparatus main body 1. A process cartridge as an image forming unit; 7, a transfer unit for transferring a toner image formed on the photosensitive drum 18 to a recording medium P; 10, a paper discharge tray on which an output image is placed; A paper feeding unit storing a recording medium P such as paper, 13 is a registration roller for conveying the recording medium P to the transfer unit 7, 15 is a manual paper feeding unit, and 18 is a photosensitive drum (photosensitive member) as an image carrier. , 19 is a developing unit housed in the process cartridge 4, 20 is a fixing unit that fixes an unfixed image on the recording medium P, 39 is an electronic member such as a control unit or an electronic board, and 41 is installed in the developing unit 19. Magnetic sensor, 50 is electronic Shows a magnetic field shielding member for covering the timber 39 and the magnetic sensor 41.

  Here, the electronic member 39 installed in the apparatus main body 1 is equipped with a control unit that performs various controls related to image formation, a power supply unit that supplies power to the transfer unit 7 and the developing unit 19, and various electronic devices. It is composed of various sensors such as an electronic substrate and a photo sensor, wiring for electrically connecting them, and the like. A magnetic field shielding member 50 that shields or attenuates a leakage magnetic field generated from the electromagnetic induction unit is installed in a part of the periphery of the electronic member 39 (on the side facing the electromagnetic induction unit of the fixing unit 20).

  Further, around the magnetic sensor 41 as an electronic member that magnetically detects the toner concentration of the developer contained in the developing unit 19 (the ratio of the toner in the developer composed of toner and magnetic carrier). In addition, a magnetic shielding member 50 that shields or attenuates a leakage magnetic field generated from the electromagnetic induction unit is provided. The toner supply amount into the developing unit 19 is determined based on the detection result of the magnetic sensor 41. That is, toner is appropriately supplied into the developing unit 19 according to the amount of toner consumed in the developing unit 19 in the developing process.

  The magnetic shielding member 50 is formed by forming a metal material such as permalloy or directional silicon steel into a plate shape. As described above, the electronic members 39 and 41 and the fixing unit 20 face each other through the metal plate having a high magnetic permeability, so that the alternating magnetic field generated from the electromagnetic induction unit can be prevented from reaching the electronic members 39 and 41. .

With reference to FIG. 1, an operation during normal image formation in the image forming apparatus will be described.
First, exposure light L such as laser light based on image information is emitted from the exposure unit 3 toward the photosensitive drum 18 of the process cartridge 4. The photosensitive drum 18 rotates counterclockwise in the drawing, and a toner image corresponding to image information is formed on the photosensitive drum 18 through a predetermined electrophotographic process (charging process, exposure process, development process). Is done.
Thereafter, the toner image formed on the photosensitive drum 18 is transferred onto the recording medium P conveyed by the registration roller 13 in the transfer unit 7.

On the other hand, the recording medium P conveyed to the transfer unit 7 operates as follows.
First, one of the plurality of paper feeding units 11, 12, and 15 of the image forming apparatus main body 1 is automatically or manually selected (for example, the uppermost paper feeding unit 11 is selected). To do.) Then, the uppermost sheet of the recording medium P stored in the paper feeding unit 11 is transported toward the position of the transport path K. Thereafter, the recording medium P passes through the conveyance path K and reaches the position of the registration roller 13. Then, the recording medium P that has reached the position of the registration roller 13 is conveyed toward the transfer unit 7 at the same timing in order to align with the toner image formed on the photosensitive drum 18.

The recording medium P after the transfer process passes through the position of the transfer unit 7 and then reaches the fixing unit 20 through the conveyance path. The recording medium P that has reached the fixing unit 20 is fed between the fixing belt and the pressure roller, and the toner image is fixed by heat received from the fixing belt and pressure received from the pressure roller. The recording medium P on which the toner image has been fixed is sent from between the fixing belt and the pressure roller, and then is discharged from the image forming apparatus main body 1 as an output image and placed on the paper discharge tray 10.
Thus, a series of image forming processes is completed.

Next, the configuration and operation of the fixing unit 20 in the image forming apparatus main body 1 will be described in detail with reference to FIG.
As shown in FIG. 2, the fixing unit 20 mainly includes a fixing auxiliary roller 21, a fixing belt 22, a heating roller 23, an electromagnetic induction unit 24, a pressure roller 30, a thermostat 37, an oil application roller 34, a guide plate 35, and a separation plate. It consists of a plate 36 and the like.

  Here, the fixing auxiliary roller 21 is formed by forming an elastic layer such as silicone rubber on the surface of a cored bar made of stainless steel or the like. The elastic layer of the auxiliary fixing roller 21 is formed to have a thickness of 5 mm and an Asker hardness of 50 degrees. The fixing auxiliary roller 21 is rotationally driven counterclockwise in FIG. 2 by a driving unit (not shown).

  The heating roller 23 includes a cylindrical portion made of iron, cobalt, nickel, or an alloy thereof. The cylindrical portion of the heating roller 23 has an outer diameter of 20 mm and a thickness of 1 mm. The heating roller 23 rotates counterclockwise in FIG. An inner core 28 made of a ferromagnetic material such as ferrite is installed inside the heating roller 23. The inner core 28 faces the coil portion 25 with the fixing belt 22 interposed therebetween.

A fixing belt 22 as a fixing member is stretched and supported by a heating roller 23 and a fixing auxiliary roller 21. The fixing belt 22 is a multilayer composed of a heat generating layer (base layer) made of a metal such as nickel, silver or iron, an elastic layer (intermediate layer) made of silicone rubber or the like, a release layer (surface layer) made of a fluorine compound or the like. It is an endless belt with a structure. The releasability for the toner T is secured by the release layer of the fixing belt 22.
As the heat generating layer of the fixing belt 22, a multi-layer structure including a resin layer such as fluorine resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, or PPS resin and a metal layer such as nickel is used. You can also.

The electromagnetic induction unit 24 includes a coil unit 25, a core 26, a coil guide 27, and the like.
Here, the coil portion 25 is wound around a litz wire bundled with fine wires so as to cover the outer peripheral portion of the fixing belt 22 wound around the heating roller 23 (in the direction perpendicular to the paper surface of FIG. 2). It is extended. The coil guide 27 is made of a resin material having high heat resistance and holds the coil portion 25. The core 26 is made of a ferromagnetic material such as ferrite, and is provided with a center core 26a and a side core 26b. The core 26 is installed so as to face the coil portion 25 extending in the width direction.

  The pressure roller 30 is formed by forming an elastic layer such as fluoro rubber or silicone rubber on a cylindrical member made of aluminum, copper or the like. The elastic layer of the pressure roller 30 is formed to have a thickness of 1 mm and an Asker hardness of 20 to 30 degrees. The pressure roller 30 is in pressure contact with the auxiliary fixing roller 21 via the fixing belt 22. Then, the recording medium P is conveyed to a contact portion (a fixing nip portion) between the fixing belt 22 and the pressure roller 30.

A guide plate 35 for guiding the conveyance of the recording medium P is disposed on the entrance side of the contact portion between the fixing belt 22 and the pressure roller 30.
A separation plate 36 that guides the conveyance of the recording medium P and promotes the separation of the recording medium P from the fixing belt 22 is disposed on the exit side of the contact portion between the fixing belt 22 and the pressure roller 30. Yes.

  An oil application roller 34 is in contact with the outer peripheral surface of the fixing belt 22. The oil application roller 34 supplies oil such as silicone oil onto the fixing belt 22. Thereby, the toner releasability on the fixing belt 22 is further ensured. The oil application roller 34 is in contact with a cleaning roller 33 that equalizes the amount of oil applied and removes dirt on the surface.

A thermostat 37 is in contact with the outer peripheral surface of the heating roller 23. Then, when the surface temperature on the heating roller 23 exceeds a predetermined temperature, the thermostat 37 cuts off the energization to the electromagnetic induction unit 24. Thereby, overheating of the heating roller 23 by the electromagnetic induction unit 24 is limited.
Although not shown, a thermistor is in contact with the outer peripheral surface of the fixing belt 22. The surface temperature (fixing temperature) on the fixing belt 22 is detected by the thermistor, and the amount of heating by the electromagnetic induction unit 24 is adjusted.

The fixing unit 20 configured as described above operates as follows.
By the rotation driving of the auxiliary fixing roller 21, the fixing belt 22 rotates in the direction of the arrow in FIG. 2, the heating roller 23 also rotates counterclockwise, and the pressure roller 30 also rotates in the direction of the arrow. The fixing belt 22 is heated at a position facing the electromagnetic induction unit 24.

  Specifically, the magnetic field lines are alternately switched between the core 26 and the inner core 28 by flowing a high-frequency alternating current of 10 kHz to 1 MHz from the power supply unit (not shown) to the coil unit 25. By forming the alternating magnetic field in this way, an eddy current is generated on the surface of the heating roller 23 and the heat generating layer of the fixing belt 22, and Joule heat is generated by the electric resistance of the heating roller 23 and the heat generating layer, and the heating roller 23 and the heating layer are heated. Thus, the fixing belt 22 is heated by the heat received from the heat roller 23 that has generated heat and the heat generated by its own heat generation layer.

Thereafter, the surface of the fixing belt 22 that generates heat by the electromagnetic induction unit 24 reaches a contact portion with the pressure roller 30. Then, the toner image T on the conveyed recording medium P is heated and melted.
Specifically, the recording medium P carrying the toner image T through the image forming process described above is fed between the fixing belt 22 and the pressure roller 30 while being guided by the guide plate 35 (indicated by the arrow Y). It is movement in the transport direction.) The toner image T is fixed to the recording medium P by the heat received from the fixing belt 22 and the pressure received from the pressure roller 30, and the recording medium P is sent from between the fixing belt 22 and the pressure roller 30.

The surface of the fixing belt 22 that has passed through the position of the pressure roller 30 then passes through the position of the oil application roller 34 and reaches the position facing the electromagnetic induction unit 24 again.
Such a series of operations is continuously repeated to complete the fixing step in the image forming process.

  In the first embodiment, the magnetic field shielding member 50 made of a high magnetic permeability material is installed on a part of the periphery of the electronic member 39 and on the side facing the electromagnetic induction portion 24 that generates an alternating magnetic field. In addition, it is possible to prevent malfunction of the electronic member 39 due to the alternating magnetic field. Similarly, since the magnetic field shielding member 50 made of a high permeability material is installed in almost the entire area around the magnetic sensor 41, malfunction of the magnetic sensor 41 due to an alternating magnetic field can be prevented in advance.

Hereinafter, the toner T used in the first embodiment will be described in detail.
The toner T is a polymerized toner and is manufactured as follows. First, a prepolymer made of a modified polyester resin, a compound that stretches or crosslinks with the prepolymer, and a toner composition are dissolved or dispersed in an organic solvent. Thereafter, the dissolved or dispersed product is subjected to a crosslinking reaction and / or an extension reaction in an aqueous medium, and the solvent is removed from the dispersion obtained therefrom to obtain a polymerized toner.

Here, in the polymerized toner, the dispersed particle diameter of the pigment-based colorant dispersed in the polymerized toner is 0.5 μm or less in number average diameter, and the number ratio of the number average diameter of 0.7 μm or more is 5 % Or less. As the colorant that is a constituent component of the polymerized toner, those having a dispersed particle diameter of 0.3 μm or less in number average diameter and a number average diameter of 10% by number or less are used.
The polymerized toner has a weight average particle size of 3.0 to 7.0 μm and a particle size distribution of 1.00 ≦ Dv / Dn ≦ 1.20 (Dv is a weight average particle size, Dn is It is a number average particle diameter.), And the circularity is 0.90 to 0.96.

The molecular weight distribution of the tetrahydrofuran-soluble component of the polyester resin contained in the polymerized toner is such that a main peak exists in the region of the molecular weight of 2500 to 10,000 and the number average molecular weight is in the range of 2500 to 50000. Is formed. This polyester-based resin has a glass transition point of 40 to 65 ° C. and an acid value of 1 to 30 mgKOH / g. The oil dispersion of the polymerized toner is obtained by dissolving an amine and a non-reactive polyester resin.
By using such a toner T, an output image with high image quality and good fixability can be obtained.

  As described above, in the configuration of the first embodiment, the magnetic field shielding member 50 is provided around the electronic members 39 and 41 without covering the fixing unit 20 with the magnetic field shielding member. Accordingly, the malfunction of the electronic members 39 and 41 due to the alternating magnetic field generated from the electromagnetic induction unit 24 can be reliably prevented without causing an abnormal temperature rise in the fixing unit 20.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 3 is a cross-sectional view showing a main part of the image forming apparatus according to the second embodiment. The image forming apparatus of the second embodiment is different from that of the first embodiment in that the image forming apparatus is a tandem color image forming apparatus and the fixing roller 31 is used as a fixing member.

  The image forming apparatus according to the second embodiment is a tandem color image forming apparatus. As shown in FIG. 3, a plurality of photosensitive drums 18BK, 18Y, 18M, and 18C are arranged in parallel on the transfer belt 8 in the image forming unit. Although not shown, a charging unit, an exposure unit, a developing unit, a cleaning unit, and a charge eliminating unit are disposed on the outer periphery of the plurality of photosensitive drums 18BK, 18Y, 18M, and 18C (process cartridge 4 in FIG. 1). Can be referred to.) Then, a toner image of each color (black, yellow, magenta, cyan) is formed on each photosensitive drum 18BK, 18Y, 18M, 18C.

The transfer unit 7 transports the recording medium P and also functions as an image carrier, a bias roller 9 that faces the photosensitive drums 18BK, 18Y, 18M, and 18C via the transfer belt 8, and a transfer belt A cleaning roller 14 for cleaning the surface of the belt 8 is formed.
The transfer belt 8 sequentially conveys the recording medium P conveyed from the direction of the arrow to a position facing each of the photosensitive drums 18Y, 18M, 18C, and 18BK. At this time, the toner images of the respective colors are transferred onto the recording medium P by the transfer bias applied to the bias roller 9. Thus, a full-color toner image is formed on the recording medium P. Thereafter, the recording medium P on which a full-color toner image is formed is separated from the transfer belt 8 and conveyed toward the fixing unit 20.

  A reflection type photosensor 43 is arranged on the outer peripheral surface of the transfer belt 8 with a gap. The photosensor 43 includes a light emitting element and a light receiving element, and detects the image density of a patch pattern formed on the transfer belt 8 at a predetermined timing. The detection result detected by the photosensor 43 is transmitted to the control unit 40 on the electronic substrate 42 via the wiring 45. The CPU of the control unit 40 obtains adjustment amounts such as a transfer bias applied to the bias roller 9 and a developing bias applied to the developing unit based on the detection result of the photosensor 43. A control signal is transmitted from the electronic substrate 42 to the power supply unit 44 (high voltage power supply unit) via the wiring 45 based on the adjustment amount of the image forming condition obtained by the control unit 40. Then, the bias applied to each member such as the bias roller 9, the cleaning roller 14, and the developing unit is adjusted by the power supply unit 44. In the second embodiment, a reflective type is used as the photosensor 43, but a transmissive type can also be used.

On the other hand, the fixing unit 20 of the second embodiment mainly includes a fixing roller 31 (fixing member), a pressure roller 30, an electromagnetic induction unit 24, and the like.
The fixing roller 31 includes a heat generating layer made of nickel or the like, an elastic layer made of silicone rubber or the like, a release layer made of a fluorine compound or the like.

  In addition, an internal core 28 is installed in the fixing roller 31 as in the heating roller 23 of the first embodiment. The electromagnetic induction unit 24 includes a coil unit 25, a core 26, and the like, as in the first embodiment. Then, when alternating current is supplied to the coil portion 25, magnetic lines of force are formed between the core 26 and the inner core 28, and the fixing roller 31 is heated by electromagnetic induction. In this way, the heated fixing roller 31 heats and fixes the toner image on the recording medium P conveyed from the direction of the arrow to the recording medium P.

  Here, the electronic members such as the photosensor 43, the control unit 40, the electronic substrate 42, the power supply unit 44, and the wiring 45 installed in the vicinity of the fixing unit 20 are each covered with a magnetic field shielding member 50. Yes. These electronic members 40, 43, 44, 45 and the magnetic field shielding member 50 are integrally installed in the transfer unit 7. That is, the transfer unit 7 including the electronic members 40, 43, 44, 45 and the magnetic field shielding member 50 is configured to be detachable from the apparatus main body 1.

  In the second embodiment, referring to FIG. 4, a box-type magnetic field shielding member 50 made of an iron plate having a plate thickness of 1 mm is used. FIG. 4 is a perspective view showing the magnetic field shielding member 50 installed around the photosensor 43. As shown in the figure, the magnetic field shielding member 50 is provided with two openings 50a and 50b. One opening 50 a is provided at a position facing the light emitting element and the light receiving element of the photosensor 43. As a result, the irradiation of the laser beam from the light emitting element of the photosensor 43 to the transfer belt 8 and the reception of the reflected light by the light receiving element of the photosensor 43 are performed without being blocked by the magnetic field shielding member 50. The other opening 50 b is provided for the wiring 45 connected to the photosensor 43. That is, the photosensor 43 is connected to the control unit 40 through the wiring 45 that passes through the opening 50b.

  As described above, in the second embodiment, the magnetic field shielding member 50 is provided around the electronic members 40, 42, 43, 44, and 45 without covering the fixing unit 20 with the magnetic field shielding member. Accordingly, the malfunction of the electronic members 40, 42, 43, 44, 45 due to the alternating magnetic field generated from the electromagnetic induction unit 24 can be reliably prevented without causing an abnormal temperature rise in the fixing unit 20.

  In the second embodiment, in the fixing unit 20, the electromagnetic induction unit 24 is opposed to the outer peripheral surface of the fixing roller 31. On the other hand, the electromagnetic induction portion can be opposed to the inner peripheral surface of the fixing roller 31. That is, the coil portion 25 can be installed inside the fixing roller 31 and the fixing roller 31 can be heated by electromagnetic induction. Naturally, the present invention can also be applied to an image forming apparatus using such a fixing unit 20, and an effect equivalent to that of the second embodiment can be obtained.

  In the second embodiment, the image forming conditions are adjusted based on the toner image (patch pattern) formed on the transfer belt 8 with the photosensor 43 facing the transfer belt 8. On the other hand, the image forming conditions can be adjusted based on the toner image formed on the photosensitive drum 18 with the photosensor 43 facing the photosensitive drum 18. Further, the image forming conditions can be adjusted based on the toner image transferred onto the recording medium P with the photosensor 43 facing the recording medium P after the transfer process. Further, in the case of a color image forming apparatus provided with an intermediate transfer belt (intermediate transfer member), the image forming conditions are adjusted based on the toner image formed on the intermediate transfer belt with the photosensor 43 facing the intermediate transfer belt. You can also

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 5 is a perspective view showing the magnetic field shielding member 50 in the third embodiment, and corresponds to FIG. 4 in the first embodiment. The magnetic field shielding member 50 of the third embodiment is different from that of the first embodiment in that a metal material is formed in a lattice shape.

As shown in FIG. 5, the magnetic field shielding member 50 is a box-shaped member having a surface in which a high permeability metal wire made of permalloy, directional silicon steel or the like is formed in a lattice shape. The lattice-shaped magnetic shielding member 50 is provided with two openings 50a and 50b as in the second embodiment.
Thus, by forming the magnetic field shielding member 50 in a lattice shape, the alternating magnetic field reaching the electronic member 43 can be reduced, and an increase in the ambient temperature of the electronic member 43 can be prevented. That is, the rise in temperature in the magnetic field shielding member 50 is reduced without hindering convection inside and outside the magnetic field shielding member 50 due to the lattice gap of the magnetic field shielding member 50.

  As described above, also in the third embodiment, by providing the magnetic field shielding member 50 around the electronic member, it is possible to reliably prevent malfunction of the electronic member due to the alternating magnetic field generated from the electromagnetic induction unit 24. Can do.

Embodiment 4 FIG.
A fourth embodiment of the present invention will be described in detail with reference to FIG.
FIG. 6 is a cross-sectional view showing the magnetic field shielding member 50 in the fourth embodiment. The magnetic field shielding member 50 of the fourth embodiment is different from those of the respective embodiments in that fins 51 as cooling means are provided on the surface thereof.

As shown in FIG. 6, a magnetic field shielding member 50 is provided around the control unit 40 as an electronic member. Further, a plurality of fins 51 as heat radiating members are provided on the outer peripheral surface of the magnetic field shielding member 50.
Thus, by installing the fins 51 in the magnetic field shielding member 50, the alternating magnetic field reaching the electronic member 40 can be reduced, and an increase in the ambient temperature of the electronic member 40 can be prevented. That is, the fins 51 of the magnetic field shielding member 50 promote heat dissipation from the surface of the magnetic field shielding member 50, and the temperature rise in the magnetic field shielding member 50 is reduced.

  In addition, by providing a blower fan or the like in the vicinity of the magnetic field shielding member 50, convection around it is promoted, and the above-described heat dissipation effect is further improved. Moreover, in this Embodiment 4, although the fin 51 was installed as a heat radiating member, a heat radiating sheet etc. can also be used instead.

  As described above, also in the fourth embodiment, by providing the magnetic field shielding member 50 around the electronic member, it is possible to reliably prevent malfunction of the electronic member due to the alternating magnetic field generated from the electromagnetic induction portion 24. Can do.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the above-described embodiments can be modified as appropriate in addition to those suggested in the above-described embodiments. Is clear. Further, the number, position, shape, and the like of the constituent members are not limited to the above-described embodiments, and the number, position, shape, and the like that are suitable for implementing the present invention can be used.

1 is a configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a cross-sectional view illustrating a fixing unit in the image forming apparatus of FIG. 1. It is a block diagram which shows the principal part of the image forming apparatus in Embodiment 2 of this invention. FIG. 4 is a perspective view showing a magnetic shielding member installed in the image forming apparatus of FIG. 3. It is a perspective view which shows the magnetic field shielding member in Embodiment 3 of this invention. It is sectional drawing which shows the magnetic field shielding member in Embodiment 4 of this invention.

Explanation of symbols

1 image forming apparatus main body (apparatus main body), 3 exposure unit,
4 Process cartridge (image forming part), 7 Transfer part,
8 transfer belt (image carrier), 9 bias roller,
18, 18BK, 18Y, 18M, 18C Photosensitive drum (image carrier),
19 developing unit, 20 fixing unit, 21 fixing auxiliary roller, 22 fixing belt,
23 heating roller, 24 electromagnetic induction part, 25 coil part,
26 cores, 28 inner cores, 30 pressure rollers, 31 fixing rollers,
39 electronic member, 40 control unit, 41 magnetic sensor, 42 electronic substrate,
43 Photosensor, 44 Power supply, 45 Wiring,
50 magnetic field shielding member, 50a, 50b opening, 51 fin (heat radiation member).

Claims (19)

An image forming apparatus including an electromagnetic induction unit that generates an alternating magnetic field in an image forming apparatus body,
An image forming apparatus, wherein a magnetic field shielding member is provided on a part or all of the periphery of an electronic member provided in the image forming apparatus main body. The image forming apparatus according to claim 1, wherein the magnetic field shielding member is provided on a side facing the electromagnetic induction unit. The image forming apparatus according to claim 1, wherein the magnetic field shielding member includes an opening. The image forming apparatus according to claim 1, wherein the magnetic field shielding member is a metal material formed in a plate shape. The image forming apparatus according to claim 1, wherein the magnetic field shielding member is a metal material formed in a lattice shape. The image forming apparatus according to claim 4, wherein the metal material is permalloy or directional silicon steel. The image forming apparatus according to claim 1, further comprising a cooling unit that cools the magnetic field shielding member. The image forming apparatus according to claim 7, wherein the cooling unit is a heat radiating member installed on a surface of the magnetic field shielding member. The electromagnetic induction unit is configured to heat the fixing member by electromagnetic induction,
The image forming apparatus according to claim 1, wherein the fixing member heats a toner image and fixes the toner image on a recording medium. The fixing member is a fixing belt stretched between a heating roller and a fixing auxiliary roller,
The heating roller is disposed so as to face the electromagnetic induction portion facing the outer peripheral surface of the fixing belt via the fixing belt,
The image forming apparatus according to claim 9, wherein the fixing auxiliary roller is disposed so as to come into contact with a pressure roller that presses a conveyed recording medium via the fixing belt. The fixing member is a fixing roller that contacts a pressure roller that presses a recording medium to be conveyed,
The image forming apparatus according to claim 9, wherein the electromagnetic induction unit faces an outer peripheral surface or an inner peripheral surface of the fixing roller. The image forming apparatus according to claim 1, wherein the electronic member is a control unit that performs control related to image formation performed in the image forming apparatus main body. 13. The image forming apparatus according to claim 1, wherein the electronic member is a power supply unit that supplies power related to image formation performed in the image forming apparatus main body. The image forming apparatus according to claim 1, wherein the electronic member is an electronic substrate on which an electronic device is mounted. The image forming apparatus according to claim 1, wherein the electronic member is a wiring for energizing. The image forming apparatus according to claim 1, wherein the electronic member is a magnetic sensor installed in a developing unit. The image forming apparatus according to claim 1, wherein the electronic member is a photosensor facing the image carrier. The image forming apparatus according to claim 17, wherein the image carrier is at least one of a photoconductor, a transfer unit, an intermediate transfer unit, and a recording medium. The image forming apparatus according to claim 1, wherein the electronic member is installed in a transfer unit or an intermediate transfer unit.

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