JP2017223819A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of suppressing an image defect by the damage of a heat application rotator without inviting a cost increase and an increase in size in the fixing device generating an AC magnetic field in a bus line direction of the heat application rotator and generating heat by an orbiting current generated by the heat application rotator.SOLUTION: In a fixing device A which includes a cylindrical heat application rotator 1 for heating a recording medium P carrying an image T and having a conductive layer 1b and has magnetic field generation means 2 and 3 for forming a magnetic field in a bus line direction X of the heat application rotator, the fixing device A allows the conductive layer 1b to generate an induction current by flowing alternate current to the magnetic field generation means and the induction current generates heat in the conductive layer. The conductive layer 1b is helically formed from one end to the other end of a base layer for a cylindrical base layer 1a, and both end parts of the conductive layer include short-circuit members 19a and 19b for being electrically conductive. The short-circuit members are electrically insulated with the conductive layer 1b in a region of a recording member passage region WB of the heat application rotator.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electromagnetic induction heating type fixing device.

  A fixing device mounted on an image forming apparatus such as an electrophotographic copying machine or a printer is a recording material that carries an unfixed toner image at a nip formed by a heating rotator and a pressure roller that contacts the heating rotator. In general, a toner image is fixed on a recording material by heating while conveying the toner.

  In recent years, electromagnetic induction heating type fixing devices capable of directly generating heat in the conductive layer of the heating rotator have been proposed, and these have the advantage that the temperature of the heating rotator increases rapidly and the power consumption is low.

  In Patent Document 1, an exciting coil and a magnetic core are arranged inside a heating rotator, an alternating magnetic field is generated in the generatrix direction of the heating rotator, and heat is generated by a circulating current generated in the circumferential direction of the heating rotator. A fixing device of the type is disclosed.

JP 2014-26267 A

  The present invention relates to a further improvement of a fixing device that directly generates heat from a conductive layer of a heating rotator as disclosed in Patent Document 1.

  In this type of fixing device, when the heating rotator breaks in a direction perpendicular to the direction of the current flowing through the heating rotator, the current concentrates at the damaged end, and the temperature rises locally. To do. The local temperature rise may cause image problems such as image unevenness and hot offset. Therefore, it is desirable to detect breakage of the heating rotator, notify the user of the phenomenon, and warn of measures such as unit replacement.

  As a means for detecting the breakage of the heating rotator, a method of detecting an abnormal temperature rise of the heating rotator using a temperature detecting element has been conventionally known. However, in order to detect an abnormal temperature rise that may occur in the entire heating rotator, it is necessary to arrange a large number of temperature detection elements in the longitudinal direction, and using such detection means increases the cost and the device. It will increase the size.

  Therefore, an object of the present invention is to provide a fixing device that can suppress image problems caused by damage to a heating rotator without increasing the cost or enlarging the device.

  A typical configuration of a fixing device according to the present invention for achieving the above object is a heating rotator for heating a recording material carrying an image, and a cylindrical heating rotator having a conductive layer; Fixing means for generating an induced current in the conductive layer by causing an alternating current to flow through the magnetic field generating means, and generating the conductive layer by the induced current. In the apparatus, the conductive layer is formed in a spiral shape from one end side to the other end side of the base layer with respect to the cylindrical base layer, and has a short-circuit member for electrically connecting both ends of the conductive layer. The short-circuit member is electrically insulated from the conductive layer in the recording material passage region of the heating rotator.

  According to the present invention, it is possible to suppress image problems due to breakage of the heating rotator without increasing the cost and increasing the size of the apparatus.

Front model diagram of main part of fixing device of embodiment 1 Cross-sectional side view of the main part of the device Perspective view of the main part of the device Explanatory drawing of the structure and manufacturing method of the fixing film in Example 1 1 is a schematic configuration diagram of an image forming apparatus using a fixing device according to a first exemplary embodiment. Explanatory drawing of the structure and manufacturing method of the fixing film in the fixing apparatus of Example 2. Perspective view of the main part of the device FIG. 6 is a perspective view of a main part of a fixing device according to a third embodiment. Front model diagram of main part of fixing device of embodiment 4 Perspective view of the main part of the device

Example 1
1. DETAILED DESCRIPTION OF THE IMAGE FORMING APPARATUS EQUIPPED WITH A FIXING DEVICE Hereinafter, embodiments of the present invention will be described based on the drawings. FIG. 5 is a schematic configuration diagram of an image forming apparatus 100 using the fixing device A of the first embodiment. The image forming apparatus 100 is an electrophotographic laser beam printer. Reference numeral 101 denotes a photosensitive drum (hereinafter referred to as a drum) as an image carrier, which is rotationally driven in a clockwise direction indicated by an arrow at a predetermined process speed (circumferential speed). The drum 101 is uniformly charged to a predetermined polarity and potential by the charging roller 102 during the rotation process.

  Reference numeral 103 denotes a laser beam scanner as image exposure means. The scanner 103 is on / off modulated in response to a digital image signal generated by the image processing unit based on image information input from an external device (not shown) such as a computer to the image processing unit (not shown). The laser beam L is output. Then, the charged surface of the drum 101 is scanned and exposed by the laser beam. By this exposure, the charge on the exposed bright portion of the drum surface is removed, and an electrostatic latent image corresponding to the image signal is formed on the drum surface.

  A developing device 104 supplies developer (toner) to the drum surface from the developing roller 104a, and the electrostatic latent image on the drum surface is sequentially developed as a toner image which is a transferable image.

  Reference numeral 105 denotes a recording material cassette in which recording materials (paper sheets) P are stacked and stored. The feeding roller 106 is driven based on the feeding start signal, and the recording material P in the cassette 105 is separated and fed one by one. The recording material P is introduced at a predetermined timing by the registration roller pair 107 into a transfer portion 108T that is a contact nip portion between the drum 101 and the transfer roller 108 that is driven to rotate in contact with the drum 101. That is, the conveyance of the recording material P is controlled by the registration roller 107 so that the leading edge of the toner image on the drum 101 and the leading edge of the recording material P reach the transfer portion 108T in synchronization.

  The recording material P is conveyed while sandwiching the transfer portion 108T, and during that time, a transfer voltage (transfer bias) controlled to a predetermined polarity with a polarity opposite to the toner charging polarity is applied to the transfer roller 108 from a transfer bias applying power source (not shown). Is done. As a result, the toner image on the drum surface side is electrostatically transferred onto the surface of the recording material P at the transfer portion 108T. The recording material P that has exited the transfer portion 108T is separated from the drum surface, passes through the conveyance guide 109, is introduced into the fixing device A, and undergoes thermal fixing processing of the toner image. The recording material P that has passed through the fixing device A is discharged from the paper discharge port 111 onto the paper discharge tray 112.

  On the other hand, the drum surface after the toner image is transferred to the recording material P is cleaned by the cleaning device 110 after removal of transfer residual toner, paper dust, and the like, and is repeatedly used for image formation. In the image forming apparatus according to the present embodiment, the recording materials having various width sizes that can be used in the apparatus are transported on the basis of the center of the recording material width center. The recording material may be conveyed on one side.

2. Outline of Fixing Device In this embodiment, the fixing device A is an electromagnetic induction heating type device. FIG. 1 is a schematic front view of a main part of the fixing device A in this embodiment, FIG. 2 is a schematic cross-sectional view of the main part of the apparatus, and FIG. 3 is a perspective view of a coil and a core part and a block diagram of a control system. is there. Here, with respect to the fixing device A, the front side is the side where the recording material P is introduced. Left and right are left (one end side) or right (other end side) when the fixing device A is viewed from the front side. The fixing device A roughly includes a heating assembly 9 as a heating member, a pressure roller 8 as a pressure member, and a device chassis (device casing: not shown) in which these are assembled.

  The heating assembly 9 includes a cylindrical heating rotating body (fixing film, fixing sleeve: hereinafter referred to as a fixing film) 1 having a conductive layer 1b (FIG. 4) described later. Further, the heating assembly 9 includes a coil (excitation coil) 3 disposed inside the fixing film 1 and a core (magnetic core) 2 disposed in a spiral portion of the coil 3. As shown in FIG. 3, the coil 3 has a spiral-shaped portion whose spiral axis is substantially parallel to the generatrix direction X of the fixing film 1, and forms an alternating magnetic field that causes the conductive layer 1b of the fixing film 1 to generate electromagnetic induction heat. . The core 2 is a member that induces magnetic field lines of an alternating magnetic field formed by the coil 3.

  The heating assembly 9 includes a film guide member 6 and a pressurizing rigid stay (hereinafter referred to as stay) 5 disposed inside the fixing film 1. The film guide member 6 is made of a heat-resistant PPS (polyphenylene sulfide) resin or the like, and is supported by the stay 5. The unit of the coil 3 and the core 2 is arranged in a space formed between both the film guide member 6 and the stay 5. Both ends of the stay 5 protrude from both ends of the fixing film 1 as shown in FIG.

  The pressure roller 8 is composed of a core metal 8a and a heat-resistant elastic material layer 8b formed and coated in a roller shape concentrically around the core metal, and a release layer 8c is provided on the surface layer. . The elastic layer 8b is preferably made of a material having good heat resistance such as silicone rubber, fluorine rubber, fluorosilicone rubber or the like. For the release layer 8c, a material having good release properties and heat resistance such as PFA, PTFE, FEP, etc. can be selected. Both ends of the cored bar 8a are disposed so as to be freely rotatable via bearings between the left and right sheet metals of the apparatus chassis.

  The heating assembly 9 is disposed substantially parallel to the pressure roller 8 with the film guide member 6 facing the pressure roller 8 above the pressure roller 8. A sliding member 7 is disposed on the lower surface of the film guide member 6.

  Then, as shown in FIG. 1, a pressing force is applied to the stay 5 by contracting the pressure springs 17a and 17b between the both ends of the stay 5 and the left and right spring receiving members 18a and 18b on the apparatus chassis side. I am letting. In the fixing device A of this embodiment, a total pressure of about 100 N to 250 N (about 10 kgf to about 25 kgf) is applied. The sliding member 7 on the lower surface of the film guide member 6 and the upper surface of the pressure roller 8 are pressed against each other with the pressing force of the stay 5 sandwiching the fixing film 1 to form a fixing nip portion N having a predetermined width in the recording material conveyance direction a. It is formed.

  The pressure roller 8 is rotationally driven in the counterclockwise direction indicated by an arrow in FIG. 2 by the driving means M, and a rotational force is applied to the fixing film 1 by a frictional force with the outer surface of the fixing film 1 in the fixing nip portion N. The fixing film 1 substantially corresponds to the rotational peripheral speed of the pressure roller 8 in the clockwise direction indicated by the arrow while the inner surface of the fixing film 1 is in close contact with the sliding member 7 on the lower surface of the film guide member 6 in the fixing nip N. It will be in a rotating state with the peripheral speed which did. The film guide member 6 guides the rotation of the fixing film 1.

  In this case, in order to reduce the mutual sliding frictional force between the lower surface of the sliding member 7 and the inner surface of the fixing film 1 in the fixing nip portion N, the lower surface of the sliding member 7 in the fixing nip portion N and the inner surface of the fixing film 1 A lubricant such as heat-resistant grease can be interposed between the two.

  The flange members 12a and 12b are externally fitted to the left and right ends of the film guide member 6, and are mounted rotatably while the left and right positions are fixed by the regulating members 13a and 13b. The flange members 12 a and 12 b receive the end of the fixing film 1 when the fixing film 1 rotates, and serve to restrict the movement of the fixing film 1 along the length of the film guide member.

  When the fixing film 1 rotates, the conductive layer 1b of the fixing film 1 generates electromagnetic induction heat (Joule heat) by an alternating magnetic field formed by an alternating current flowing through the coil 3. This heat is transmitted to the later-described elastic layer 1c (FIG. 4) laminated on the outer surface of the conductive layer 1b and the release layer 1d laminated on the outer surface, whereby the entire fixing film 1 is heated.

  TH is a temperature detection element (temperature detection element: temperature detection means) such as a non-contact thermistor for detecting the surface temperature of the fixing film 1. The temperature detection element TH is arranged to be held by a holding means (not shown) so as to detect the temperature of the longitudinal center portion of the fixing film 1 upstream of the fixing nip portion N in the recording material conveyance direction a. Detection temperature information of the temperature detection element TH is input to the control unit 15. Based on the detected temperature information input from the temperature detecting element TH, the control unit 15 raises and maintains the surface temperature of the fixing film 1 at a predetermined target temperature (about 150 ° C. to 200 ° C.). To control the power supplied to the coil 3.

  As described above, the pressure roller 8 is driven to rotate, and the fixing film 1 is driven to rotate. As a result, the fixing film 1 is fixed from the image forming unit side in a state where the temperature of the fixing film 1 is raised and regulated. A recording material P carrying an unfixed toner image T is introduced into the nip portion N. The recording material P is nipped and conveyed by the fixing nip portion N, and is heated by the heat of the fixing film 1 and receives a nip pressure. As a result, the unfixed toner image T is fixed to the recording material P by heat and pressure as a fixed image.

3. Configuration and Manufacturing Method of Fixing Film The configuration and manufacturing method of the fixing film 1 will be described with reference to FIG. As shown in the schematic cross-sectional view of FIG. 4C, the fixing film 1 includes a cylindrical base layer 1a made of an insulating member, a conductive layer 1b formed in a spiral shape on the outer surface, and an outer surface. This is a cylindrical rotating body having a composite structure of a laminated elastic layer 1c and a release layer 1d laminated on the outer surface thereof.

  The base layer 1a is made from an insulating heat-resistant resin such as polyimide, polyamideimide, PEEK, PES, etc., and is molded into a cylindrical shape with a thickness of 30 μm to 100 μm. In this example, the base layer 1a was manufactured by molding a polyimide resin into a cylindrical shape having an inner diameter of 30 mm, a width (longitudinal length) WA of 240 mm, and a thickness of 60 μm.

  The conductive layer 1b is a conductive layer made of iron, copper, silver, aluminum, nickel, chromium, tungsten, an alloy such as SUS304 or nichrome containing these, or a conductive resin such as CFRP (carbon fiber reinforced plastic) or carbon nanotube resin. Wire is used. This wire is formed by forming a spiral on the outer peripheral surface of the base layer 1a.

  FIG. 4A shows a perspective view of a state in which the conductive layer 1b is formed by spirally winding a conductive wire around the outer peripheral surface of the base layer 1a. The conductive layer 1b formed in a spiral shape has a spiral shape portion whose spiral axis is substantially parallel to the generatrix direction X of the cylindrical base layer 1a, and the spiral shape portion extends over almost the entire width WA of the base layer 1a. Is formed.

  The conductive layer 1b can also be formed by applying a conductive paste containing silver, carbon fiber, carbon nanotube, or the like as a filler to the base layer 1a in a spiral shape. The helical pitch interval of the conductive layer 1b optimum for the heat generation principle described later varies depending on the volume resistivity and diameter (layer thickness) of the conductive member used. In addition, the diameter (layer thickness) of the conductive member and the helical pitch interval are also limited due to the following reasons.

  That is, if the diameter (layer thickness) of the conductive member is too large, the uneven shape cannot be absorbed by the elastic layer 1c, resulting in uneven hardness of the fixing film 1, and uneven pressure due to the uneven hardness may appear as image unevenness. Therefore, the diameter (layer thickness) of the conductive member is preferably 200 μm or less.

  On the other hand, if the helical pitch interval is too large, the surface temperature of the fixing film 1 when the conductive layer 1b is directly below and the surface temperature when the conductive layer 1b is not present become heat unevenness, and in this case, it may appear as image unevenness. Therefore, the spiral pitch interval is preferably 500 μm or less.

  Table 1 shows a list of conductive member names, volume resistivity, diameter, and optimum helical pitch intervals for each member within a range where such image unevenness does not occur.

  In the present embodiment, a conductive member is provided with a diameter as a conductive member at one side end (one end side) of a core (not shown) inserted into the hollow portion of the cylindrical base layer 1a so that the base layer 1a is not deformed when the conductive layer 1b is formed. The end portion of the conductive wire made of 50 μm SUS304 is bonded with the heat resistant adhesive 1e. Then, a conductive wire is wound around the base layer 1a toward the other end portion at a spiral pitch interval of 100 μm by an axial turning method. Thus, a spiral conductive layer 1b was created. The end point at the end of winding was adhered to the other end portion (the other end side) of the side surface of the base layer 1a with a heat resistant adhesive 1f.

  In contrast to the base layer 1a in which the spiral conductive layer 1b is formed on the outer peripheral surface as shown in FIG. 4A, the recording material of the maximum width size usable in the apparatus as shown in FIG. The elastic layer 1c and the release layer 1d were formed in the region WB corresponding to the passing region. In this embodiment, the recording material of the maximum width size that can be used in the apparatus is a letter size (width 216 mm), and the width of the region WB is set to 220 mm, which is slightly larger than the letter size width 216 mm. Hereinafter, this area WB is referred to as a recording material excess area (maximum passage area).

  Then, due to the difference between the width WA of the base layer 1a and the width of the recording material excess area WB, the elastic layer 1c and the release layer 1d each having a width of 10 mm are formed on one end side and the other end side of the base layer 1a. An annular conductive layer exposed portion (hereinafter referred to as a conductive region) WC / WC is provided.

  In this example, the elastic layer 1c was formed by spray coating to form a silicone rubber having a hardness of 20 degrees (JIS-A, 1 kg load) with a thickness of 300 μm (where the conductive layer 1b is not present is 350 μm). The elastic layer 1c plays a role of suppressing the pressure unevenness and heat unevenness of the conductive layer 1b described above, and the optimum elastic layer 1c varies depending on the diameter and the helical pitch of the elastic layer 1c. Then, a fluororesin tube having a thickness of 30 μm was coated as a release layer 1d on the elastic layer 1c by a heat shrink method. The release layer 1d plays a role of preventing the fixing film from being stained due to adhesion of toner or paper powder.

4). FIG. 3 shows a perspective view and a control block diagram of the core 2 and the coil 3 constituting the magnetic field generating means (magnetic field generating means) for induction heating the fixing film 1, the fixing film 1. The core 2 has a cylindrical shape, and is disposed through a hollow portion of the fixing film 1 by a fixing means (not shown). The magnetic field lines (magnetic fluxes) generated by the alternating magnetic field generated by the coil 3 are guided to the inside of the fixing film 1 and function as members that form magnetic field line paths (magnetic paths).

  The material of the core 2 is desirably formed of a material having a small hysteresis loss and a high relative permeability. For example, it is a ferromagnetic material composed of a high-permeability oxide or alloy material such as sintered ferrite, ferrite resin, amorphous alloy (amorphous alloy), or permalloy. Preferably, the cross-sectional area should be as large as possible within a range that can be stored in the fixing film 1 that is a cylindrical member. The shape is not limited to a cylindrical shape, and a prismatic shape or the like can be selected.

  The coil 3 is formed by winding a normal single conducting wire in a spiral shape with about 10 to 40 windings around the core 2 in the hollow portion of the fixing film 1. In this embodiment, the number of windings is 18 times. Inside the cylindrical rotating body, it is wound in a direction crossing the rotation axis. In other words, the coil 3 has a spiral portion whose spiral axis is substantially parallel to the generatrix direction X of the fixing film 1. For this reason, when a high-frequency current is passed through the coil 3 via the high-frequency converter 14 and the power supply contact portions 3a and 3b, a magnetic field can be generated in a direction parallel to the generatrix direction X of the fixing film 1 as a cylindrical rotating body. .

  The basic heat generation principle of the induction heating type fixing apparatus A configured as described above is the same as that of the transformer. That is, the coil 3 corresponds to the primary coil (18 turns) on the input side, and the fixing film 1 corresponds to the secondary coil on the output side. When an alternating voltage V1 of about 21 kHz to 50 kHz is applied to the primary coil (coil 3), a current I1 flows through the primary coil.

  As a result, a magnetic flux generated in a direction parallel to the generatrix direction X of the fixing film 1 flows into the core 2, and an induced electromotive force V <b> 2 is generated in the secondary coil (fixing film 1) by the magnetic flux, and the conductive layer 1 b of the fixing film 1 is generated. A current I2 flows along.

  The first part that generates heat in the system in which induction heating is performed is heat generation of the coil 3 due to copper loss in the copper wire of the primary coil. The second is the heat generation of the fixing film 1 due to copper loss in the copper wire of the secondary coil (fixing film 1). The third is the heat generation of the magnetic core 2 due to Joule heat loss and hysteresis loss generated inside the magnetic core 2. In the fixing device A of the present embodiment, the first and third heat generations cause energy loss. Therefore, the heat generation is suppressed as much as possible, and the fixing film 1 is heated using the second copper loss. It is what I did.

  As described above, in the fixing film 1 of the present embodiment, the elastic layer 1c and the release layer 1d are formed in the recording material passage region WB, and outside the region, that is, on one end side and the other end side of the fixing film 1. In each of the circumferential directions, annular conductive regions WC and WC are formed. As a result, the conductive layer 1b of the fixing film 1 is configured to be electrically connected to a short-circuit member described later in the conductive region WC on one end side and the conductive region WC on the other end side. And in the state which the both ends of the conductive layer 1b are short-circuited, when an alternating magnetic flux acts, an induced current will generate | occur | produce in the conductive layer 1b and the conductive layer 1b will generate | occur | produce heat.

  By adopting such a configuration, when the fixing film 1 is damaged and a part of the conductive layer 1b or the short-circuit member is disconnected, the induced current does not flow throughout the conductive layer 1b, and the heat generation of the fixing film 1 is automatically performed. To stop. Therefore, the local temperature rise due to the breakage of the fixing film 1 does not occur in the fixing device of the present embodiment, and the fixing device configuration does not cause image adverse effects such as image unevenness and hot offset.

5. Fixing Film Breakage Detection Method As shown in FIGS. 1 and 3, both ends of the conductive layer 1 b of the fixing film 1 are used as short-circuit members in the conductive region WC on one end side and the conductive region WC on the other end side of the fixing film 1. The conductive brushes 19a and 19b are electrically connected. The amount of induced current flowing through the conductive layer 1b is detected by a current detector (current detection means) 10. The control unit 15 can control the high-frequency converter 14 based on the induced current amount detected by the current detector 10.

  Thus, the control unit 15 can determine that the fixing film 1 is abnormal when the fixing film 1 indicates a value other than the amount of induced current set so as to be maintained and adjusted at a predetermined target temperature. When the fixing film 1 is damaged and the conductive layer 1b or the conductive brushes 19a and 19b are partially disconnected, the induced current does not flow. Thereby, the presence or absence of breakage of the fixing film 1 can be detected. The control unit 15 can notify the user of the abnormality by operating the notification unit 20. That is, the control unit 15 is a determination unit that determines whether there is an abnormality in the fixing film 1 according to the detection information of the current detector 10.

  By adopting the configuration as described above, it is possible to provide a fixing device that can suppress image problems caused by damage to the fixing film 1 without increasing the cost or enlarging the device.

Example 2
The structure of the fixing film 30 used in Example 2 is shown in FIG. A spiral conductive layer 30b made of the same conductive wire as that shown in FIG. 4A is formed on a cylindrical polyimide base layer 30a having a diameter of 30 mm, a width (longitudinal length) WA of 230 mm, and a thickness of 60 μm. A conductive short-circuit wire 30g coated with heat-resistant insulation was joined to both ends of the conductive layer 30b. FIG. 6A is a perspective view thereof. The conductive portions at both ends of the short-circuit wire 30g are joined to both ends of the conductive layer 30b outside the recording material passage region WB (220 mm) by the high melting point solders 30e and 30f on one end side and the other end side of the base layer 30a. Therefore, it is configured to be electrically conductive.

  That is, the short-circuit wire 30g is electrically insulated from the conductive layer 30b by the heat-resistant insulating coating in the recording material passage region WB of the fixing film 30. The conductive layer 30b and the short-circuit line 30g may have any configuration as long as they are not conductive in the region of the recording material maximum passage region WB. For example, a configuration in which the heat-resistant insulating coating around the conductive wire used for forming the conductive layer 30b is used and the heat-resistant insulating coating of the short-circuit wire 30g is eliminated may be used. In this embodiment, SUS304 having a diameter of 50 μm, which is the same as that of the conductive layer 30b, is coated with a heat-resistant insulating coating.

  6B is a perspective view of the fixing film 30, and FIG. 6C is a cross-sectional view of the fixing film 30. The fixing film 30 is formed by using the same members and methods as those of the fixing film 1 of Example 1 with respect to the base layer 30a in which the spiral conductive layer 30b is formed on the outer peripheral surface as shown in FIG. The elastic layer 30c and the release layer 30d were formed as in (b) and (c).

  In the second embodiment, since both ends of the conductive layer 30b are electrically connected to each other by the short-circuit wire 30g in the fixing film 30, the fixing film 30 does not need to be configured to be electrically connected to other members. Therefore, as shown in FIG. 6B, the elastic layer 30c and the release layer 30d were formed so as to cover the entire area of the conductive layer 30b.

  By using the fixing film 30 for the fixing device A, the fixing device can be made smaller than in the first embodiment. That is, as in the fixing film 1 of the first embodiment, the conductive brushes 19a and 19b are not provided on the outer peripheral surface, and the conductive regions WC and WC that can be electrically connected to both ends of the fixing film 1 are not provided. The fixing device can be made smaller than 1.

  FIG. 7 is a perspective view and a control block diagram of the core 2, the coil 3, and the fixing film 30 for inductively heating the fixing film 30 in the second embodiment. The high-frequency converter 14 is provided with a power detection unit (power detection means) 31 so that the power consumed by the fixing film 30 can be detected. The control unit 32 can control the high-frequency converter 14 based on the power consumption detected by the power detection unit 31.

  Accordingly, the control unit 32 can determine that the fixing film 30 is abnormal when the fixing film 30 indicates a value other than the power consumption set so as to be maintained and adjusted to a predetermined target temperature. When the fixing film 30 is damaged and a part of the conductive layer 30b or the short-circuit line 30g is disconnected, no induced current flows through the conductive layer 30b, so that no power is consumed by the fixing film 30. Therefore, it is possible to detect whether the fixing film 30 is damaged or not, and the control unit 15 can operate the notification unit 20 to notify the user of the abnormality. That is, the control unit 32 is a determination unit that determines whether there is an abnormality in the fixing film 30 according to the detection information of the power detection unit 31.

  By adopting the configuration as described above, it is possible to provide a fixing device capable of suppressing image damage caused by damage to the fixing film 30 without increasing the cost or increasing the size of the device even in a configuration in which the fixing device A is downsized. it can.

Example 3
In the second embodiment, it is possible to detect whether or not the fixing film 30 is damaged by a temperature detection element (temperature detection means) TH that detects the temperature of the fixing film 30 instead of the power detection unit 31. That is, the temperature detecting element TH for temperature control described above can be used as a breakage detecting means for the fixing film 30.

  FIG. 8 is a perspective view and a control block diagram of the core 2, the coil 3, and the fixing film 30 for inductively heating the fixing film 30 in the second embodiment. The control unit 41 can control the high frequency converter 14 based on the surface temperature of the fixing film 30 detected by the temperature detection element TH. Accordingly, the control unit 41 can determine that the fixing film 30 is abnormal when the fixing film 30 shows a value other than the predetermined target temperature.

  When the fixing film 30 is damaged and a part of the conductive layer 30b or the short-circuit line 30g is disconnected, an induced current does not flow through the conductive layer 30b, and the heat generation of the fixing film 30 is stopped. Therefore, it is possible to detect whether or not the fixing film 30 is damaged, and the control unit 41 can operate the notification unit 20 to notify the user of the abnormality. That is, the control unit 32 is a determination unit that determines whether there is an abnormality in the fixing film 30 according to detection information of the temperature detection element TH.

  As described above, even in the configuration using the temperature detecting means TH, it is possible to provide a fixing device that can suppress image problems due to damage to the fixing film 30.

Example 4
Usually, a fixing device mounted on an image forming apparatus such as a copying machine or a printer has a heating area having a width corresponding to the maximum width size usable in the apparatus. For this reason, when a small size recording material narrower than the width of the heating area is continuously printed, the non-passing area temperature rise (non-passing area where the recording material of the heating rotator does not pass (non-sheet passing area) excessively increases It is known that the temperature rise of the paper passing part) occurs. If the non-passage area of the heating rotator is excessively heated, the heating rotator itself, the holder for holding the heating rotator, and the pressure roller may be damaged by heat. The configuration is more preferable.

  In the fixing device having the configuration of Example 2, the fixing film 1 of Example 1 is used instead of the fixing film 30, and the metal rod 50 that also functions as a soaking member is used as the short-circuit member. . As a result, it is possible to impart an effect of suppressing the temperature increase of the non-passing portion to the short-circuit member.

  The method for detecting whether or not the fixing film 1 is broken is the same as that in the second embodiment, and is omitted in this example. The details of the temperature-inhibiting effect of the non-passing portion of the short-circuit member that also functions as a soaking member are described below.

  FIG. 9 is a schematic front view of the fixing device A according to the fourth embodiment, in which an aluminum metal rod 50 is disposed as a short-circuit member. FIG. 10 is a perspective view of the main part of the fixing device. Both ends of the metal rod 50 are grooves provided in flange members 51a and 51b on one end side and the other end side that restrict the movement of the fixing film 1 in the thrust direction. It is rotatably held by 52a and 52b. Therefore, the metal rod 50 is driven to rotate in accordance with the rotation of the fixing film 1 that is in contact therewith.

  One end side and the other end side of the metal rod 50 are respectively in contact with the annular conductive regions WC and WC at the one end side and the other end side of the fixing film 1, and the metal rod 5 is at both ends of the conductive layer 1 b of the fixing film 1. It plays the role of electrically conducting the part.

  FIG. 10 is a schematic diagram showing a difference in diameter in the longitudinal direction of the metal rod 50. The metal rod 50 is in contact with the release layer 1d of the fixing film 1 in the recording material passage area WB (220 mm), but in contact with the conductive layer 1b in the conductive areas WC and WC, the elastic layer 1c and the release layer 1d. The diameter is increased by the thickness of. In the present embodiment, the diameter of the metal bar 50 in the recording material passage area WB is 5.0 mm, and the diameter of the metal bar 50 in the conductive areas WC and WC is 5.3 mm.

  That is, in the fourth embodiment, the metal rod 50 as the short-circuit member also serves as a heat equalizing member that equalizes the temperature distribution along the length of the recording material passage region WB of the fixing film 1. In order to confirm the effect of this example, the fixing device without the heat equalizing member of Example 2 was used as a comparative example, and the recording material non-passing portion temperature rise of the fixing device of Example 4 was compared. Fifty sheets of B5 size (width 182 mm) small size recording materials were continuously introduced (passed through) into a fixing device corresponding to the letter size (width 216 mm) as the maximum width size recording material. The surface temperature of the fixing film in this case was photographed using an infrared thermography R300SR manufactured by Nippon Avionics Co., Ltd.

  The surface temperature of the fixing film in the passage region of the small size recording material is set to 170 ° C. Table 2 shows the result of comparing the maximum temperature of the fixing film in the non-passing portion after the continuous introduction of 50 sheets in the comparative example and the present example 4. In the fixing device of Example 4, the non-passing portion temperature is 10 ° C. lower than that of the comparative example, which indicates that the configuration of Example 4 is effective for increasing the temperature of the non-passing portion.

  As described above, it is possible to provide a fixing device that can suppress the adverse effect of an image due to breakage of the heating rotator even in the configuration using the member that also serves as the heat equalizing member as the short-circuit member.

  In the first to fourth embodiments described above, the fixing device that fixes the unfixed toner image T to the recording material P has been described as an example. However, in the present invention, the invention is not limited to this, and in order to improve the gloss of the image, a device that heats and presses the toner image fixed on the recording material or the assumed toner image (also referred to as a fixing device in this case) is used. Is equally applicable.

  A ... Fixing device 1. Heating rotating body 2. 3. Magnetic field generating means (magnetic core and excitation coil) 1a ... Cylindrical base layer 1b ... Helical conductive layer 19a .19b..Short-circuit member, WB..Recording material passage area, P..Recording material, T ..

Claims (5)

A heating rotator for heating a recording material carrying an image, comprising: a cylindrical heating rotator having a conductive layer; and a magnetic field generating means for forming a magnetic field in a generatrix direction of the heating rotator, wherein the magnetic field In the fixing device in which an induced current is generated in the conductive layer by passing an alternating current through the generating means, and the conductive layer generates heat by the induced current.
The conductive layer is spirally formed from one end side to the other end side of the base layer with respect to the cylindrical base layer,
A short-circuit member for electrically conducting both ends of the conductive layer;
The fixing device according to claim 1, wherein the short-circuit member is electrically insulated from the conductive layer in a recording material passage region of the heating rotator.   The current detection means for detecting a current flowing through the conductive layer, and a determination means for determining the presence or absence of an abnormality of the heating rotator according to detection information of the current detection means. Fixing device.   The power detection means for detecting the power consumed in the conductive layer, and the determination means for determining the presence / absence of abnormality of the heating rotator according to the detection information of the power detection means. The fixing device described.   The temperature detection means for detecting the temperature of the heating rotator, and the determination means for determining the presence or absence of abnormality of the heating rotator according to the detection information of the temperature detection means. Fixing device.   The fixing device according to claim 1, wherein the short-circuit member also serves as a heat equalizing member that equalizes a temperature distribution along a length of the recording material passage region of the heating rotator.