JP4034275B2 - Induction heating apparatus and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a fixing device in dry electrophotographic equipment, a drying device in wet electrophotographic equipment, a drying device in an ink jet printer, an induction heating device suitably used for an erasing device for rewritable media, and an image including the induction heating device. The present invention relates to a forming apparatus.

  In a heating device, for example, a fixing device in dry electrophotographic equipment, a drying device in wet electrophotographic equipment, a heating device for an erasing device for rewritable media, a halogen lamp is provided inside a heating roller having a hollow metal core such as aluminum, A configuration in which a heating roller is heated by a halogen lamp has been widely used. The method using such a halogen lamp has a problem that the rise at the start of heating is slow and the warm-up time is long.

  Therefore, an induction heating device in which a conductive layer is provided on the heating roller, an alternating magnetic field is applied to the conductive layer by a magnetic field generating means to generate eddy current, and the heating roller (heating member) is heated by Joule heat generated by this eddy current is attracting attention. Has been. Although this induction heating device is excellent in heating efficiency, in order to shorten the warm-up time and further improve the convenience, it is necessary to reduce the heat capacity of the heating member. However, when the heat capacity of the heating member is reduced, it becomes difficult to move the temperature of the heating member in the longitudinal direction, and it is difficult to make the temperature distribution in the longitudinal direction of the heating member uniform. Various proposals have been made as techniques for improving these.

  For example, in order to reduce the temperature drop that occurs at the folded portion of the induction coil, it has been proposed that the folded portion of the induction coil has a laminated structure (see, for example, Patent Document 1). According to this proposed technology, the magnetic flux generated at the folded portion of the magnetic field generating means is strengthened and can be linked to the heating member, so the amount of heat generated at the flux linkage is increased and temperature drop is improved. can do. In addition, since the length of the induction coil in the longitudinal direction can be made shorter, it is possible to achieve downsizing of the fixing device, and hence the image forming apparatus including the fixing device.

As another improvement technique, by providing a U-shaped magnetic flux concentrating member at the folded portion of the induction coil, the magnetic flux is linked from the end of the folded portion of the induction coil to the heating member. There has also been proposed a technique for improving the temperature distribution in the longitudinal direction of the heating member by increasing the calorific value of the folded portion (see, for example, Patent Document 2).
JP 2002-43049 A JP 2002-222687 A

  By the way, in the structure described in Patent Document 1, in order to reduce the warm-up time and further improve convenience, when the heat member is made to have a low heat capacity by using a belt, the end of the folded portion of the induction coil is used. Although the temperature of the portion is high, there is a problem that a region having a temperature lower than the central portion of the magnetic field generating means and the end portion of the folded portion is spot-likely generated at a position inside thereof.

  Further, even when the magnetic flux concentrating member described in Patent Document 2 is used, the temperature drop at the end of the folded portion of the induction coil can be improved, but the spot between the end of the folded portion and the central portion of the magnetic field generating means is described above. With regard to the temperature drop that occurs automatically, there is a problem that the spot-like temperature drop cannot be suppressed because the magnetic flux interlinking with the heating member in the region cannot be adjusted. In addition, the magnetic flux concentrating member described in Patent Document 2 has a complicated shape and is difficult to manufacture and install.

  The present invention has been made to solve such a problem, and suppresses a drop in temperature generated at the folded portion of the magnetic field generating means when the heating member is induction-heated by the magnetic field generating means having the folded portion. An induction heating device capable of improving the temperature uniformity in the longitudinal direction of the heating member, and an image having an induction heating device having such characteristics and capable of outputting a high-quality image An object is to provide a forming apparatus.

An induction heating apparatus according to the present invention includes a heating member having a conductive layer that generates heat in a varying magnetic field, a magnetic field generation unit that generates a magnetic field that generates heat from the heating member, and a magnetic flux concentration that controls the magnetic field generated by the magnetic field generation unit. And the magnetic field generating means is disposed so as to surround a part of the outer peripheral portion of the heating member, and the heat of the heating member is not covered by the magnetic field generating means of the heating member. It is premised on an induction heating device configured to transmit heat to a material to be heated .

  The operation of the induction heating apparatus of the present invention will be described below.

  First, the magnetic field generating means applied to the induction heating device corresponds to both ends of the magnetic field generating means because the heating member (heating roller) to be heated often has a structure that is long in the longitudinal direction (axial direction). There is a region where the direction of the magnetic field suddenly reverses in the folded portion. In the reversal region, the magnetic field interlinking with the heating member continuously changes and does not align in one direction, so the amount of heat generation is reduced compared to other parts where the direction of the magnetic field is aligned, and the temperature in the longitudinal direction A phenomenon that the uniformity is deteriorated occurs. In order to make the heating device more compact, such a phenomenon reduces the waiting time when the folded portion of the magnetic field generating unit is stacked so that the length of the magnetic field generating unit approaches the maximum printable paper width. For this reason, it becomes particularly remarkable when the heating member has a low heat capacity and the heating member is heated to a predetermined temperature in a short time.

  In order to solve the above-described problems related to temperature uniformity in the longitudinal direction, in the induction heating device of the present invention, the magnetic flux concentrating member is aligned in the magnetic field direction in the region corresponding to the folded portion where the magnetic field direction changes. Since the magnetic flux in the region where the direction of the magnetic field continuously changes is not reinforced, the temperature drop is reduced. In addition, since the magnetic fields having the same orientation are effectively linked to the heating member, the amount of heat generated in the portion increases, and the temperature uniformity in the longitudinal direction (axial direction) of the heating member can be easily improved. become.

  In addition, if the magnetic flux concentrating member is arranged in a parallel region extending parallel to the longitudinal direction of the heating member, it is possible to effectively interlink the heating member with a high-quality magnetic flux in which the direction of the magnetic field is aligned. The temperature distribution in the direction can be improved.

  Note that even if the magnetic flux concentrating member is disposed in a region where the direction of the generated magnetic field continuously changes, that is, a region having a curvature (curved portion) among the regions corresponding to the folded portion of the magnetic field generating means, that portion is originally a magnetic field. Since the direction of the magnetic flux is not uniform, the magnetic flux concentrating member uniformly strengthens the weakened magnetic flux, so that the magnetic flux distribution linked to the heating member is not stabilized and the heat generation distribution can be adjusted effectively. Can not.

In the induction heating apparatus of the present invention, the magnetic field generating means is a parallel region portion extending in parallel with the longitudinal direction of the heating member, and an annular member having folded portions formed at both ends of the parallel region portion, as described above. , flux concentration member, the direction of the magnetic field generated in the folded portion of the magnetic field generating means that are arranged in a region are aligned in a certain direction. In this case, the magnetic flux concentrating member is integrally formed with an opposing portion arranged to face the outer surface of the folded portion of the magnetic field generating means and an approach portion extending from the opposing portion to a position approaching the heating member. that has been formed. Thus, by using the magnetic flux concentrating member having the approaching portion to the heating member, it is possible to easily adjust the magnetic flux distribution linked to the heating member, and to improve the uniformity of the heating member.

  Further, in this case, the distance D (see FIG. 13) between the surface of the approaching portion of the magnetic flux concentrating member facing the peripheral portion of the magnetic field generating means and the peripheral portion of the magnetic field generating means is set as the folded portion of the magnetic field generating means. If it is set based on the curvature of the existing bent portion, the uniformity of the temperature distribution of the heating member can be further improved.

  That is, the folded portion of the magnetic field generating means generally has a radius of curvature of about 3 mm to 5 mm depending on the specifications, and the direction of the magnetic field continuously changes in the folded portion having the radius of curvature. Therefore, the longitudinal direction of the heating member is reduced by reducing the influence of the region where the direction of the magnetic field is not uniform in the folded portion by installing the magnetic flux concentrating member close to the heating member at a distance of 5 mm or more from the magnetic field generating means. The temperature distribution in the (axial direction) can be made more uniform and stable.

In the induction heating device of the present invention, the first magnetic flux concentrating member disposed in a region where the direction of the magnetic field is aligned in the gap existing between the folded portion of the magnetic field generating means and the heating member Another second magnetic flux concentrating member is disposed, and the second magnetic flux concentrating member is disposed at a predetermined distance (at least 5 mm or more) from the approaching portion of the first magnetic flux concentrating member . . As described above, when the second magnetic flux concentration member is disposed in the gap portion existing between the folded portion of the magnetic field generating means and the heating member, the gap portion of the magnetic flux interlinking with the heating member is arranged in the gap portion. Since the magnetic flux at the interlinked portion can be strengthened, it is possible to increase the amount of heat generated in the inner region of the folded portion of the magnetic field generating means, that is, the region where temperature drop is likely to occur, and the temperature uniformity can be further improved. .

  Further, a distance X (see FIG. 16) between the approaching portion of the first magnetic flux concentrating member and the second magnetic flux concentrating member is 5 mm or more (a surface facing the peripheral portion of the magnetic field generating means of the approaching portion of the first magnetic flux concentrating member) And at least the same dimension as the distance D between the magnetic field generating means and the peripheral edge of the magnetic field generating means), the influence of the magnetic flux generated at the folded portion can be suppressed, and the amount of heat generation further increases.

  In the dielectric heating device according to the present invention, when the third magnetic flux concentrating member is arranged in a parallel region portion of the magnetic field generating means and in a region close to the turned-up portion, the high-quality magnetic flux having the same orientation is reinforced and heated. The members can be linked to each other. As a result, it is possible to further increase the amount of heat generated in the portion where the temperature drop occurs, and to further improve the temperature distribution uniformity in the longitudinal direction.

  In the induction heating apparatus of the present invention, the magnetic field generating means is constituted by a conducting wire (heating coil) that extends in parallel with the longitudinal direction of the heating member and is folded and wound at both ends in the longitudinal direction, and the folded portion. A configuration may be adopted in which a plurality of conducting wires are laminated and the number of laminated conducting wires in the folded portion is larger than the number of laminated conducting wires in the parallel region portion. By adopting such a configuration, the region where the direction of the magnetic field is perpendicular to the longitudinal direction and the direction of the magnetic field is aligned can be made longer (wider) in the folded portion of the magnetic field generating means. As a result of the magnetic flux strengthened by the member having a better quality with more uniform orientation, the temperature uniformity can be further improved.

  Furthermore, in the folded portion of the magnetic field generating means, the region where the magnetic field in the direction perpendicular to the longitudinal direction is uniformly generated, that is, the region in which the conductors of the folded portion are formed in parallel is, for example, the direction perpendicular to the longitudinal direction. If the thickness is 8 mm or more, the temperature distribution in the longitudinal direction can be further improved because the magnetic field direction is hardly affected by the continuous change.

  Moreover, since the distance in the longitudinal direction of the magnetic field generating means becomes shorter by using the magnetic field generating means in which the folded portions are laminated, the heating device can be reduced in size. Further, since the distance in the longitudinal direction of the folded portion of the magnetic field generating means is shortened, the arrangement of the second magnetic flux concentration member is facilitated.

  In the present invention, the image forming apparatus may be configured by using the induction heating device having the above characteristics as a fixing device. In this case, since the temperature uniformity in the longitudinal direction of the heating member can be improved, an image forming apparatus capable of forming a high-quality image can be provided.

  The induction heating device of the present invention is a device that induction-heats a heating member with a magnetic field generating means having a folded portion, and is an area in which the direction of the magnetic field generated by the magnetic field generating means is aligned in a certain direction, particularly the generation of a magnetic field. Since the magnetic flux concentrating member is arranged in the region where the direction of the magnetic field generated in the folded portion of the means is aligned in a certain direction, the temperature drop generated in the folded portion of the magnetic field generating means can be suppressed, and the heating member The temperature uniformity in the longitudinal direction can be easily improved.

  According to the image forming apparatus of the present invention, since the induction heating apparatus having the above-described features is provided, an image with high quality can be output.

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

  First, an example of a fixing device to which the induction heating device of the present invention is applied will be described with reference to FIG.

  The fixing device 10 in this example includes a heating roller (heating member) 1 having a conductive layer (metal layer) that is a heat generating layer, a magnetic field generating unit 2 disposed outside the heating roller 1, a pressure roller 3, and a magnetic field generating unit. 2 includes an excitation circuit 4 for applying a high-frequency current to a heating element 1 and a temperature detection element (for example, a thermistor) 5 for detecting the temperature of the heating roller 1. The heating roller 1 is heated to a constant temperature by the magnetic field generating means 2. By passing the recording paper (heated material) P having an unfixed toner image through the contact portion (nip portion N) between the heated heating roller 1 and the pressure roller 3, the recording paper P This is a device for fixing an image on the screen.

  Next, components constituting each part of the fixing device 10 will be briefly described.

  The heating roller 1 has a heat insulating elastic layer (heat-resistant sponge layer), a conductive layer (metal sleeve), an elastic layer on a core metal (either hollow or solid) such as iron, stainless steel, or aluminum. And the surface release layer is laminated | stacked in this order. Specifically, as shown in FIG. 2, the heating roller 1 includes a heat insulating elastic layer 1b, a metal sleeve 1c that is a heat generation layer, an elastic layer 1d, and a release layer 1e on a metal core 1a such as aluminum. It is a laminated structure.

  The metal sleeve 1c is a heating element that generates heat by induction heating, and the thickness is reduced to 30 μm to 200 μm in order to shorten the rise time of the surface temperature.

  Since the metal sleeve 1c is heated by induction heating, it may be any conductive member having magnetism such as iron or stainless steel (SUS430). In particular, the relative permeability may be high, and for example, a silicon steel plate, an electromagnetic steel plate, nickel steel, or the like may be used. Moreover, even if it is a non-magnetic material, since it can be induction-heated if it is a material with high resistance values, such as stainless steel (SUS430), you may use this. Furthermore, even if it is a non-magnetic base member (for example, a heat-resistant resin such as ceramic and polyimide), if the material having a high relative permeability is disposed so as to have conductivity, It may be used. Moreover, in order to increase the calorific value, a composite material made of a plurality of materials may be used. In this example, a nickel material having a thickness of 40 μm is used for the heat generating layer (metal sleeve 1c).

  The heat insulating elastic layer 1b is disposed to prevent heat escape from the metal sleeve 1c, which is a heating element, and to suppress deformation of the metal sleeve 1c. In this example, a heat-resistant silicone sponge is used.

  An elastic layer 1d and a release layer 1e are formed on the metal sleeve 1c.

  The release layer 1 e plays a role of preventing the toner having a lowered viscosity that is heated at the nip portion N (see FIG. 1) from adhering to the heating roller 1. As a material for the release layer 1e, PFA (a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether), PTFE (polytetrafluoroethylene), or the like is used.

  The elastic layer 1d is provided to improve the adhesion between the melted toner and the release layer 1e. As the material of the elastic layer 1d, heat-resistant silicon rubber (LTV, RTV, HTV) or the like is used. In this example, PFA is used for the release layer 1e, and heat-resistant silicon rubber (LTV) is used for the elastic layer 1d.

  The pressure roller 3 is a member for forming a nip portion N that contacts the heating roller 1 and passes the recording paper P.

  The pressure roller 3 is configured to have a heat-resistant elastic layer (not shown) such as silicon rubber on an iron / stainless steel or aluminum cored bar. The pressure roller 3 is pressed against the heating roller 1 by an unillustrated elastic member (spring), thereby forming a nip portion N having a width of about 7 mm with the heating roller 1. A release layer made of PFA or PTFE may be formed on the surface of the pressure roller 3.

  The magnetic field generating means 2 for heating the heating roller 1 is constituted by a heating coil 2a as shown in FIG. 3, and is arranged so as to surround the outer peripheral portion of the heating roller 1 as shown in FIG. If the heating coil 2a is arranged outside the heating roller 1 in this way, the heating coil 2a can be easily cooled with respect to the radiant heat from the heating roller 1, so that the heating value of the heating coil 2a itself that increases when the temperature becomes high (copper) Loss) can be suppressed to prevent a reduction in heating efficiency. In FIG. 4, the entire configuration of the magnetic field generating means 2 is schematically shown without showing the winding state of the heating coil 2 a constituting the magnetic field generating means 2.

  A heat resistant material is used as the material of the heating coil 2a. In this example, 30 litz wires (twisted enamel wires or the like) are used, each having 30 insulated wires with a diameter of 0.3 mm. In order to suppress the copper loss generated in the heating coil 2a, the total resistance value of the heating coil 2a is 0.5Ω or less, preferably 0.1Ω or less. A plurality of heating coils 2a may be arranged according to the size of the recording paper P to be fixed.

  An alternating magnetic field is generated by applying a high-frequency current of 20 kHz or more to the heating coil 2a by the excitation circuit 4 and the generated alternating magnetic field is linked to the heating roller 1 so that the heating roller 1 is induction-heated. The The temperature control of the heating roller 1 is performed by adjusting the output of the excitation circuit 4 according to the detection signal of the temperature detection element 5 arranged in the vicinity of the entrance of the nip portion N. A series of temperature detection and temperature control by power control are controlled by a control circuit unit (not shown) provided in the excitation circuit 4.

  In this way, the heating roller 1 controlled to a constant temperature is rotated by a rotating mechanism (not shown), so that the recording paper P having an unfixed toner image is passed through the nip portion N, and the toner image is transferred. It can be fixed on the recording paper P by heat and pressure.

  Next, the heating operation of the heating roller 1 will be described.

  First, during warm-up, the excitation circuit 4 connected to the heating coil 2a is turned on, and the heating coil 2a is excited. As a result, an alternating eddy current is induced in the metal sleeve (conductive layer) 1c of the heating roller 1, and heat is generated by Joule heat. The amount of heat generated at this time is about 900 W. At the same time as the energization by the excitation circuit 4 is started, the pressure roller 3 is driven to rotate by rotating the heating roller 1. The surface temperature of the heating roller 1 is constantly detected by the temperature detecting element 5, and when the surface temperature of the heating roller 1 reaches a predetermined temperature (180 ° C. in this example), the warm-up is completed, and the heating circuit 2 supplies the heating coil 2 a by the excitation circuit 4. Is switched to on-off control, and the surface temperature of the heating roller 1 is maintained at a predetermined temperature.

  Then, the recording paper P on which the unfixed toner image is transferred is conveyed to the contact nip portion N, and the toner image is melted and fixed by the heat of the heating roller 1 and the pressure of the pressure roller 3, and is fixed on the recording paper P and fastened. It becomes a correct image.

Next, the basic configuration of the induction heating apparatus of the present invention will be described below.

< Basic configuration >
First, the magnetic field generating means 2 has a structure in which the heating coil 2a is wound as described above. As shown in FIG. 4, the parallel region portion 21 extending in parallel to the longitudinal direction (axial direction) of the heating roller 1 and its parallel portion. It is an annular member in which folded portions 22 are formed at both ends of the region portion 21, and an opening 23 is formed in the center.

  The arrangement position and the effect when the magnetic flux concentrating member is arranged in the magnetic field generating means 2 will be described with reference to FIGS.

  FIG. 5 is a diagram showing a form in which the magnetic field generating means 2 is separated into regions by paying attention to the direction of the generated magnetic field, and the part (A) shows that the heating coil 2a is installed in a direction perpendicular to the longitudinal direction. In this region, the direction of the generated magnetic flux is aligned in a direction parallel to the longitudinal direction. The part (B) is an area where the heating coil 2a is installed substantially parallel to the longitudinal direction, and the direction of the generated magnetic flux is aligned perpendicular to the longitudinal direction. The portion (C) is a bent portion at the end of the folded portion 22, and the heating coil 2a is bent with a predetermined curvature, and the direction of the generated magnetic flux continuously changes.

  FIG. 6 shows in detail how the direction of the magnetic field continuously changes as the position of the magnetic field generating means 2 changes from (B) → (C) → (A). Thus, in the portion (C) of the magnetic field generating means 2, the curvature of the heating coil 2 a is different between the inside and the outside of the magnetic field generating means 2, and the direction of the generated magnetic field is also the inside and outside of the magnetic field generating means 2. I can see that they are different.

  Thus, in the part (C) of the magnetic field generating means 2, a magnetic field with a fixed direction is not generated. Therefore, even if a magnetic flux concentrating member is arranged in the part (C), the magnetic field having a different direction is strengthened as it is. Therefore, it is impossible to improve the temperature drop caused by the different direction of the magnetic field.

  On the other hand, if a magnetic flux concentrating member is arranged in the portion (A) or (B) of the magnetic field generating means 2, a magnetic flux having a good quality with a uniform magnetic field direction can be effectively linked to the heating roller 1. It becomes like this. Therefore, as shown in FIG. 7, by disposing the magnetic flux concentrating member 6 in the portion (A) or (B) of the magnetic field generating means 2, the amount of heat generation can be effectively increased, and the heating roller 1 ( The temperature distribution in the longitudinal direction of FIG. 4) can be improved.

  Here, as the magnetic flux concentrating member, a material having a high relative magnetic permeability and high electrical conductivity is suitable. For example, ferrite (nickel-zinc-based, copper-zinc-based), silicon steel plate or electromagnetic steel plate is used. can do. In this example, nickel-zinc ferrite is used.

8 and 9 are a perspective view and a side view showing the configuration of another embodiment of the magnetic flux concentrating member . In FIG. 9B, the magnetic field generating means and the magnetic flux concentration member are shown in a cut state.

  In this example, the magnetic flux concentrating member 11 is arranged in the portion (A) shown in FIG. 5, that is, the region where the direction of the magnetic field generated in the folded portion 22 of the magnetic field generating means 2 is aligned (substantially the central portion of the folded portion 22). And a magnetic flux concentrating member 11 which is disposed opposite the outer surface (upper surface) of the folded portion 22 of the magnetic field generating means 2 and an end portion (magnetic field generating means) of the opposing portion 11a. 2 is an L-shaped member integrally formed with an approach portion 11b extending from the end portion on the opening side to the position approaching the heating roller 1.

  In this way, the L-shaped magnetic flux concentrating member 11 is arranged in the portion (A) of the magnetic field generating means 2, and the approaching portion 11 b of the magnetic flux concentrating member 11 is the portion where the temperature starts to drop, that is, inside the magnetic field generating means 2. By arranging in the portion (inside the opening 23 of the magnetic field generating means 2), the magnetic flux linked to the heating roller 1 is strengthened, and the amount of heat generated in the portion is increased, so the temperature distribution in the longitudinal direction of the heating roller 1 is increased. Can be improved.

  The shape of the magnetic flux concentrating member having an approaching portion that approaches the heating roller 1 is not only the L shape as shown in FIGS. 8 and 9, but also approaching both ends of the facing portion 11a ′ as shown in FIG. A U-shaped magnetic flux concentrating member 11 ′ provided with a portion 11 b ′ may be used. Moreover, you may use the magnetic flux concentration member of a structure as shown to Fig.11 (a)-(g).

  Each of the examples of FIGS. 11A and 11F is a magnetic flux concentrating member having the same structure as that shown in FIGS. 8 and 9, and is characterized in that an approaching portion to the heating roller 1 is integrally formed.

  Each of the examples in FIGS. 11B and 11G is an L-shaped and U-shaped magnetic flux concentrating member, and is characterized in that the facing portion and the approaching portion are formed of separate members.

  Each of the examples of FIGS. 11 (c) and 11 (d) changes the magnetic flux distribution interlinked with the heating roller 1 by partially changing the cross-sectional area of the portion through which the magnetic flux passes in the U-shaped magnetic flux concentrating member. It is characterized in that the structure is changed.

  In the example of FIG. 11 (e), in the U-shaped magnetic flux concentrating member, the approaching part e1 approaching the heating roller 1 and the approaching part e2 have different lengths, so that the magnetic flux distribution linked to the heating roller 1 is changed. It is characterized in that the structure is changed. In the example of FIG. 11 (e), it is preferable to shorten the length of the approaching part e1 disposed in the opening 23 of the magnetic field generating means 2 out of the two approaching parts e1 and e2.

  As described above, the temperature distribution can be improved by changing the shape of the magnetic flux concentrating member in accordance with the degree of temperature drop generated in the inner portion of the folded portion 22 of the magnetic field generating means 2.

Next, a specific configuration of the induction heating apparatus of the present invention will be described below.
<Embodiment 1 >
This example is characterized in that the positional relationship between the L-type magnetic flux concentrating member 11 and the magnetic field generating means 2 is defined in the configuration shown in FIGS. The specific positional relationship will be described with reference to FIGS.

In the example shown in FIG. 12, the approaching portion 11 b of the L-shaped magnetic flux concentrating member (first magnetic flux concentrating member described in claims) 11 is spaced a predetermined distance from the inner peripheral edge of the magnetic field generating means 2. It is characterized by the arrangement. Further, in such an arrangement, as shown in FIG. 13, the distance between the approaching portion 11b of the magnetic flux concentrating member 11 and the inner peripheral edge of the magnetic field generating means 2 is D, and the folded portion of the magnetic field generating means 2 is used. When the radius of curvature of the curved portion existing at 22 is R, the distance D between the approaching portion 11b and the magnetic field generating means 2 is set so as to satisfy the condition of D ≧ R.

  Specifically, the innermost side R of the magnetic field generating means 2 is often about 2 mm to 5 mm due to structural limitations, and the outermost side R of the magnetic field generating means 2 is The distance D between the approaching portion 11b and the magnetic field generating means 2 is set in a range of 5 mm to 30 mm, so that the folded portion 22 of the magnetic field generating means 2 The influence of the generated magnetic flux can be suppressed, and the amount of heat generated in the folded portion 22 can be increased to improve the temperature distribution in the longitudinal direction. In this example, the approach part 11b of the magnetic flux concentrating member 11 is installed at a position where D = 12 mm.

<Embodiment 2 >
14 and 15 are an exploded perspective view and a perspective view showing the configuration of another embodiment of the present invention. FIG. 16 is a side view of the embodiment.

  In this example, the L-shaped first magnetic flux concentrating member is located in the portion (A) of the magnetic field generating means 2 shown in FIG. 5, that is, the region where the direction of the magnetic field of the folded portion 22 is aligned (substantially the central portion of the folded portion 22). 11 and the second magnetic flux concentrating member (flat plate shape) 12 in the gap S (see FIG. 16) existing between the folded portion 22 of the magnetic field generating means 2 and the heating roller 1. The first magnetic flux concentrating member 11 is characterized in that it is installed at a predetermined distance from the approaching portion 11b.

  As described above, when the second magnetic flux concentrating member 12 is installed between the folded portion 22 of the magnetic field generating means 2 and the heating roller 1, as shown in FIG. 16, in the vicinity of the inside of the folded portion 22 of the magnetic field generating means 2. It becomes possible to locally strengthen the magnetic flux in the part where the temperature starts to drop. Thereby, since the calorific value of the part increases, the temperature distribution in the longitudinal direction can be improved.

  Here, when the second magnetic flux concentrating member 12 is installed, the distance (interval) X (see FIG. 16) between the second magnetic flux concentrating member 12 and the approaching portion 11b of the first magnetic flux concentrating member 11 is the heating roller. Necessary for strengthening the interlinkage magnetic field to 1 and increasing the amount of heat generation, the distance X is not less than the distance D shown in FIG. 13 and within the distance to the end 2e of the magnetic field generating means 2. Thus, the temperature distribution can be effectively improved without strengthening the uneven magnetic field generated at the folded portion 22 of the magnetic field generating means 2. In this example, the distance X is 13 mm.

  If the first magnetic flux concentrating member 11, the second magnetic flux concentrating member 12, and the magnetic field generating means 2 are held by the holding member 14 having a structure as shown in FIG. The positional relationship with the concentration members 11 and 12 can be maintained with high accuracy. Note that the holding member 14 shown in FIG. 17 is provided with a position regulating rib 14 a for determining the position of the holding member 14.

  As the material of the holding member 14, since it is necessary to have excellent insulation and heat resistance, polyimide (PI), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polycarbonate (PC), etc. It is preferable to use engineering plastics represented by

<Embodiment 3 >
FIG. 18 is a perspective view of the main part showing the configuration of another embodiment of the present invention.

In this example, the first magnetic flux concentrating member 11 and the second magnetic flux concentrating member 12 are arranged in a predetermined positional relationship in the folded portion 22 of the magnetic field generating means 2 (shown as <Embodiment 1 > and <Embodiment 2 >). The third magnetic flux concentrating member 13 is characterized in that it is disposed in the parallel region portion 21 of the magnetic field generating means 2 and in the vicinity of the folded portion 22.

By arranging the third magnetic flux concentrating member 13 in this way, it is possible to reinforce the high-quality magnetic flux having the same orientation and to link it to the heating roller 1, so that the amount of heat generated in the portion where the temperature drop occurs can be reduced. Furthermore, the temperature distribution uniformity in the longitudinal direction can be further improved.

-Example-
In the example shown in FIG. 18, a structure in which the heating coil 2 a of the folded portion 22 of the magnetic field generating means 2 is stacked is used, and a roller using a 40 μm nickel belt is used as the heating roller 1. When the temperature distribution in the axial direction (longitudinal direction) of the heating roller 1 was measured for the case where the first to third magnetic flux concentrating members 11 to 13 were installed and the case where the magnetic flux concentrating member was not installed, FIG. The results as shown in Fig. 1 were obtained.

  As is apparent from the results of FIG. 19, the temperature distribution in the axial direction (longitudinal direction) of the heating roller 1 is improved by arranging the first to third magnetic flux concentration members 11 to 13 in a predetermined positional relationship. You can see that

<Embodiment of Image Forming Apparatus>
FIG. 20 is a diagram schematically showing an example of a color image forming apparatus to which the induction heating device of the present invention is applied.

  The color image forming apparatus 100 in this example is a so-called tandem printer in which four color visible image forming units 100Y, 100M, 100C, and 100B are arranged along a recording medium conveyance path. Specifically, four sets of visible image forming units 100Y, 100M, 100C, and 10B are arranged along a conveyance path of the recording paper P that connects the supply tray 120 of the recording paper P (material to be heated) and the fixing device 10. Then, after each color toner is multiplex-transferred onto the recording paper P conveyed by the recording paper conveying means 130 of the endless belt, it is fixed by the fixing device 10 which is an embodiment of the induction heating device of the present invention, and a full color image is obtained. Is formed. The fixing device 10 has basically the same configuration as that of the example shown in FIG. 1, and a magnetic flux concentration member as shown in FIGS. 7 to 18 is arranged.

  Next, the configuration of each part of the color image forming apparatus 100 will be described.

  The recording paper conveyance means 130 has an endless conveyance belt 133 that is stretched by a pair of drive rollers 131 and idling rollers 132 and that rotates by being controlled at a predetermined peripheral speed (134 mm / s in this example). The recording paper P is electrostatically adsorbed onto the conveying belt 133 and conveyed.

  Each of the visible image forming units 100Y, 100M, 100C, and 100B includes a photoreceptor drum 111, and around the photoreceptor 111, a charging roller 112, a laser beam irradiation unit 113, a developing device 114, and a transfer roller. 115 and cleaner 116 are arranged in this order.

  The developing devices 114 of the visible image forming units 100Y, 100M, 100C, and 100B contain yellow (Y), magenta (M), cyan (C), and black (B) toners. Each of the visible image forming units 100Y, 100M, 100C, and 100B forms a toner image on the recording paper P by the following process.

  That is, after the surface of the photosensitive drum 111 is uniformly charged by the charging roller 112, the surface of the photosensitive drum 111 is laser-exposed according to image information by the laser light irradiation unit 113 to form an electrostatic latent image. Thereafter, the developing device 114 develops a toner image on the electrostatic latent image on the photosensitive drum 111, and the visualized toner image is transferred to the transfer roller 115 to which a bias voltage having a polarity opposite to that of the toner is applied. Transfer is sequentially performed on the recording paper P conveyed by the conveying means 130.

  The recording paper P onto which the toner image has been transferred is peeled off from the transport belt 133 by the curvature of the drive roller 131 and then transported to the fixing device 10. Therefore, an appropriate temperature and pressure are given by the heating roller 1 and the pressure roller 3 maintained at a predetermined temperature. Then, the toner is dissolved and fixed on the recording paper P to form a robust image. Here, in the color image forming apparatus 100 of this example, the temperature uniformity in the longitudinal direction of the heating roller 1 of the fixing device 10 can be improved, so that high-quality image formation can be performed.

  The induction heating device of the present invention is not limited to the fixing device described above, but can also be used as a heating device such as a drying device in a wet electrophotographic apparatus, a drying device in an inkjet printer, or an erasing device for rewritable media. .

  The induction heating device of the present invention can be effectively used as a fixing device in dry electrophotographic equipment, a drying device in wet electrophotographic equipment, a drying device in an ink jet printer, or an erasing device for rewritable media.

1 is a diagram schematically illustrating an example of a fixing device to which the present invention is applied. FIG. 2 is an enlarged cross-sectional view schematically showing a main part structure of a heating roller used in the fixing device of FIG. 1. It is a perspective view which shows the structure of the heating coil of the magnetic field generation means used for the fixing device of FIG. It is a perspective view which shows the attachment state to the heating roller of the magnetic field generation means of FIG. It is a figure for demonstrating the area | region suitable for arrangement | positioning of a magnetic flux concentration member with the perspective view of a magnetic field generation means. It is a figure which shows the direction of the magnetic flux generated by a magnetic field generation means. It is a perspective view which shows the state which has arrange | positioned the magnetic flux concentration member in the magnetic field generation means. Is an exploded perspective view showing the configuration of implementation of the invention. Is a side view showing the structure of implementation of the invention. It is a figure which shows the other example of a magnetic flux concentration member. It is a figure which shows another example of a magnetic flux concentration member. It is a perspective view which shows the positional relationship of a L-type magnetic flux concentration member and a magnetic field generation means. It is a side view which shows the positional relationship of a L-type magnetic flux concentration member and a magnetic field generation means. It is a disassembled perspective view which shows the structure of another embodiment of this invention. It is a perspective view which shows the structure of another embodiment of this invention. It is a side view which shows the structure of another embodiment of this invention. It is sectional drawing which shows the holding structure of a magnetic flux concentration member and a magnetic field generation means. It is a perspective view which shows the structure of another embodiment of this invention. It is a figure which shows temperature distribution when the magnetic flux concentration member is installed and when the magnetic flux concentration member is not installed. 1 is a diagram schematically illustrating a configuration of an embodiment of an image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fixing device 1 Heating roller 1a Core metal 1b Thermal insulation elastic layer 1c Metal sleeve (conductive layer)
DESCRIPTION OF SYMBOLS 1d Elastic layer 1e Surface release layer 2 Magnetic field generating means 2a Heating coil 21 Parallel region part 22 Folding part 23 Opening part 3 Pressure roller 4 Excitation circuit 5 Temperature detection element (thermistor)
6 Magnetic flux concentrating member 11 L-shaped magnetic flux concentrating member (first magnetic flux concentrating member)
11a Opposing part 11b Approaching part 12 Second magnetic flux concentrating member 13 Third magnetic flux concentrating member 14 Holding member S Gap part P Recording paper 100 Image forming apparatus 100Y, 100M, 100C, 100B Visible image forming unit 111 Photosensitive drum 112 Charging roller 113 Laser light irradiation means 114 Developer 115 Transfer roller 116 Cleaner

Claims (5)

A heating member having a conductive layer that generates heat in a variable magnetic field, a magnetic field generating unit that generates a magnetic field that generates heat from the heating member, and a first magnetic flux concentrating member that controls the magnetic field generated by the magnetic field generating unit , The magnetic field generating means is disposed so as to surround a part of the outer peripheral portion of the heating member, and heat of the heating member is used as a material to be heated at a portion of the heating member that is not surrounded by the magnetic field generating means. In an induction heating device configured to communicate,
The magnetic field generating means is an annular member in which a parallel region portion extending in parallel with the longitudinal direction of the heating member and a folded portion are formed at both ends of the parallel region portion,
The first magnetic flux concentrating member is disposed in a region where the direction of the magnetic field generated in the folded portion of the magnetic field generating means is aligned in a certain direction, and faces the outer surface of the folded portion of the magnetic field generating means. And a facing portion that extends to a position approaching the heating member from the facing portion, and a facing portion that is disposed in an integrated manner,
A second magnetic flux concentrating member different from the first magnetic flux concentrating member is disposed in a gap existing between the folded portion of the magnetic field generating means and the heating member. The member is arranged with a predetermined distance from the approaching portion of the first magnetic flux concentrating member . The distance between the surface of the approaching portion of the magnetic flux concentrating member facing the peripheral edge of the magnetic field generating means and the peripheral edge of the magnetic field generating means is based on the curvature of the bent portion existing in the folded portion of the magnetic field generating means. induction heating apparatus according to claim 1, characterized in that it is set. The induction heating device according to claim 1 or 2 , wherein a third magnetic flux concentrating member is installed in a region close to the folded portion in the parallel region portion of the magnetic field generating means . The magnetic field generating means is constituted by a conductive wire that extends parallel to the longitudinal direction of the heating member and is folded and wound at both ends in the longitudinal direction, and the conductive wire is laminated at the folded portion, and the folded portion. induction heating apparatus according to any one of claims 1 to 3, the number of stacked conductors is characterized in that it is more than the number of stacked conductors of the parallel area section. An image forming apparatus comprising the induction heating device according to claim 1.

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