JP2012118391A - Induction heat unit, fixing device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation in fixing quality due to aging regardless of a long period of use of an induction heat unit employing the configuration in which an excitation coil is stuck to a coil bobbin as the induction heat unit.SOLUTION: An induction heat unit 170 with a fixing part for heating a conductive fixing belt 154 through electromagnetic induction and thermally fixing a toner image to a recording sheet comprises: a coil bobbin 171 disposed in the axial direction of the fixing belt 154 and in its longitudinal direction; an excitation coil 173 formed by winding a Litz wire 181 and stuck to the holding surface 171a of the coil bobbin 171 with an adhesive 183. The adhesive 183 is elastic, and is partially applied to a predetermined area of the holding surface 171a of the coil bobbin 171.

Description

  The present invention relates to an induction heating unit, a fixing device, and an image forming apparatus, and more particularly to a technique for suppressing deterioration in fixing quality over time.

Conventionally, some image forming apparatuses such as printers employ a fixing device that thermally fixes a toner image to a recording sheet by electromagnetic induction heating (for example, Patent Document 1).
Such a fixing device has an advantage that energy saving can be achieved as compared with a fixing device using a halogen heater as a heat source.
FIG. 13A is a cross-sectional view showing a configuration of a conventional electromagnetic induction type fixing device 500, and FIG. 13B is a partially enlarged view thereof.

As shown in FIG. 5A, the fixing device 500 includes an induction heating unit 540, a fixing roller 550 provided with a heat generating layer 553 on the outer periphery, and a pressure roller 560.
The induction heating unit 540 includes an exciting coil 573, a coil bobbin 571 that holds the exciting coil 573, and an arch magnetic body core 574 made of a ferromagnetic material.
The coil bobbin 571 has a holding surface 572 that holds the exciting coil 573. The holding surface 572 is curved along the outer peripheral surface of the heat generating layer 553 so that the distance between the excitation coil 573 and the heat generating layer 553 held therein is uniform.

  The exciting coil 573 has a Joule heat generated by energizing the litz wire 535a after winding the litz wire 535a, the surface of which is coated with the thermal adhesive 573b, around a winding jig (not shown) having the same shape as the coil bobbin 571. Thus, the thermal fusing agent 573b is temporarily melted, so that the adjacent litz wires 535a are thermally fused to fix the shape.

As shown in FIG. 13 (b), the exciting coil 573 has a coil bobbin through an adhesive 580 in which the concave surface of the two surfaces formed by winding the litz wire 535a is applied to the entire surface. It is joined to the holding surface 572 of 571.
Since the holding surface 572 of the coil bobbin 571 is disposed in parallel with the axis of the fixing roller 550, the distance between the exciting coil 573 and the heat generating layer 553 adhered and held on the holding surface 572 is the distance from the exciting coil 573 to the heat generating layer 553. The magnetic flux density acting on the toner is uniform in the axial direction of the fixing roller 550 (hereinafter referred to as the “longitudinal direction”), thereby preventing the heat generation layer 553 from generating uneven heat.

JP 2008-139448 A

However, it has been found that when the induction heating unit 540 having such a configuration is used for a long period of time, the central portion in the longitudinal direction of the coil bobbin 571 is deformed into a shape that bends toward the fixing roller 550 side.
This is because the exciting coil 573 has a slightly larger linear expansion coefficient than that of the coil bobbin 571, and therefore, a large thermal stress is generated to cause the coil bobbin 571 to bend in the longitudinal direction where the elongation amount due to the expansion is particularly large. It is considered that the coil bobbin 571 is plastically deformed by being repeated.

When such plastic deformation occurs, the magnetic flux density acting on the heat generating layer 553 in the longitudinal direction of the coil bobbin 571 becomes non-uniform, causing heat generation unevenness and lowering the fixing quality.
The present invention has been made in view of the above-described problems, and prevents the coil bobbin from being deformed by long-term use of the induction heating unit, so that the fixing quality does not deteriorate, the fixing device, and the image formation An object is to provide an apparatus.

  In order to achieve the above object, an induction heating unit according to the present invention is an induction heating unit in a fixing device that heats a conductive heat generating rotator by electromagnetic induction to thermally fix a toner image on a recording sheet. A coil bobbin disposed in the longitudinal direction along the axial direction of the rotating body, and an exciting coil formed by winding a conductive wire and adhered to a coil holding surface of the coil bobbin with an adhesive, and the adhesive is It has elasticity in a solidified state and is partially applied to a predetermined region of the coil holding surface.

  In the exciting coil, since the adhesive has elasticity and the adhesive is only partially bonded to a predetermined region of the coil holding surface of the coil bobbin, the longitudinal extension of the exciting coil caused by thermal expansion is prevented. It can be easily released by elastic deformation of the adhesive, and the thermal stress applied in the longitudinal direction of the coil bobbin is greatly relieved. For this reason, even when used for a long period of time, plastic deformation hardly occurs in the coil bobbin, and uneven heat generation does not occur.

The predetermined region preferably includes at least regions corresponding to both ends of the coil in the longitudinal direction.
Furthermore, it is desirable that the application area per unit area of the adhesive on the coil holding surface of the adhesive is equal to or greater than the other regions in the regions corresponding to both ends in the longitudinal direction of the coil.

Here, it is preferable that the adhesive is applied in a line on the coil holding surface.
For example, the adhesive may be applied to the coil holding surface so that its application shape is a zigzag shape or a meandering shape in a single stroke state.
Alternatively, the application shape of the adhesive may be a stripe shape.

Alternatively, the excitation coil is wound in an oval shape, and the adhesive is provided along the first path provided along the inner periphery of the excitation coil and the outer periphery of the excitation coil. It is good also as apply | coating along the 2nd path | route provided.
Moreover, it is desirable to provide unevenness on the coil holding surface of the coil bobbin to increase the contact area with the adhesive.

Here, the unevenness may be formed by performing a blasting process on the coil holding surface.
The adhesive may be applied in the form of dots.
The adhesive is preferably a silicone adhesive.
Moreover, it is desirable to provide a pressing means for pressing the entire exciting coil or a specific portion toward the coil holding surface of the coil bobbin.

Here, the pressing means is a net having elasticity and heat resistance, which is attached to a coil bobbin so as to cover the exciting coil in a state having tension, and the exciting coil is connected to the coil by the net. You may comprise so that it may hold down toward a holding surface.
Alternatively, the pressing means includes a pressing member provided so as to follow the shape of the surface of the excitation coil opposite to the surface attached to the coil holding surface, and the excitation coil via the pressing member. An urging means for urging in the coil holding surface direction may be included.

Moreover, it has a lid member mounted so as to cover the exciting coil, and the urging means may be an elastic member interposed in a compressed state between the lid member and the pressing member.
Alternatively, the pressing means includes a pressing member provided so as to follow the shape of the surface of the excitation coil opposite to the surface attached to the coil holding surface, and between the pressing member and the excitation coil. And the pressing member is attached to the coil bobbin in a state in which the sheet-like elastic member is compressed, so that the exciting coil is caused by the elastic force of the elastic member. May be configured to be urged directly in the coil holding surface direction.

The coil bobbin preferably has a positioning portion that contacts the edge of the excitation coil and positions the excitation coil.
Here, the positioning portion is a recess provided on the coil holding surface of the coil bobbin along the shape of the excitation coil, and the excitation coil is positioned by fitting the excitation coil into the recess. Is desirable.

Furthermore, it is preferable that the positioning portion is a protrusion standing on a coil holding surface of the coil bobbin, and the excitation coil is positioned by abutting the protrusion on an edge of the excitation coil.
Note that the present invention may be a fixing device including the induction heating unit, or may be an image forming apparatus including the fixing device.

1 is a schematic diagram for explaining a configuration of a tandem type color printer that is an example of an image forming apparatus including an induction heating unit according to an embodiment of the present invention. FIG. 3 is a partially cutaway perspective view showing a configuration of a fixing device including the induction heating unit. (A) is a see-through | perspective plan view which shows the structure of the said induction heating unit, (b) is the D-D 'sectional drawing, (c) is the principal part enlarged view of (b). FIG. 2 is a partial cross-sectional view illustrating a configuration of a fixing belt of the fixing device. (A) is a figure which shows the application condition of the adhesive agent of the coil bobbin of the said induction heating unit, (b) is an expanded sectional view of the adhesive agent coating surface. (A) And (b) is a figure explaining the deformation | transformation condition of an adhesive agent when both an exciting coil and a coil bobbin thermally expand in a different ratio in the said induction heating unit. (A) is a figure which shows the application condition of the adhesive agent of the coil bobbin which concerns on the modification of this invention, (b) is a figure which shows the application order of the said adhesive agent. It is a figure which shows the application | coating condition of the adhesive agent of the coil bobbin which concerns on the modification of this invention. It is a figure which shows the application | coating condition of the adhesive agent of the coil bobbin which concerns on the modification of this invention. (A) is a top view which illustrates the structure of the induction heating unit which concerns on the modification of this invention, (b) is the E-E 'sectional drawing. (A) is a top view which illustrates the structure of the induction heating unit which concerns on the modification of this invention, (b) is the FF 'sectional drawing, (c) is FIG. It is JJ 'sectional drawing of a). (A) And (b) is sectional drawing which illustrates the structure of the induction heating unit which concerns on the modification of this invention. (A) is sectional drawing which illustrates the structure of the conventional induction heating unit, (b) is the principal part enlarged view.

Hereinafter, embodiments of an induction heating unit, a fixing device, and an image forming apparatus according to the present invention will be described with reference to the drawings.
<Configuration of image forming apparatus>
FIG. 1 is a schematic diagram for explaining a configuration of a tandem type color printer (hereinafter simply referred to as “printer”) as an example of an image forming apparatus including an induction heating unit according to an embodiment of the present invention.

  As shown in FIG. 1, the printer 1 includes an image processing unit 3, a paper feeding unit 4, a fixing unit 5, an optical unit 10, and a control unit 60. The printer 1 is connected to a network (for example, a LAN) and connected to an external device. When a print job execution instruction is received from a terminal device (not shown), a toner image composed of yellow, magenta, cyan and black is formed based on the instruction, and a full-color image is formed by multiple transfer of these toner images. .

Hereinafter, the reproduction colors of yellow, magenta, cyan, and black are represented as Y, M, C, and K, and Y, M, C, and K are added as subscripts to the numbers of the components related to the reproduction colors.
The image processing unit 3 includes image forming units 30Y, 30M, 30C, and 30K, an optical unit 10, an intermediate transfer belt 11, and the like corresponding to Y to K colors.
The image forming unit 30Y includes a photosensitive drum 31Y, a charger 32Y disposed around the photosensitive drum 31Y, a developing unit 33Y, a primary transfer roller 34Y, a cleaner 35Y for cleaning the photosensitive drum 31Y, and the like. A Y-color toner image is formed on the drum 31Y. The other image forming units 30M to 30K have the same configuration as that of the image forming unit 30Y, and the reference numerals are omitted in FIG.

The intermediate transfer belt 11 is an endless belt, is stretched around a driving roller 12 and a driven roller 13, and is rotationally driven in the direction of arrow A.
The optical unit 10 includes a light emitting element such as a laser diode, emits a laser beam L for forming an image of Y to K colors by a drive signal from the control unit 60, and exposes and scans the photosensitive drums 31Y to 31K.

By this exposure scanning, electrostatic latent images are formed on the photosensitive drums 31Y to 31K charged by the chargers 32Y to 32K. The electrostatic latent images are developed by developing units 33Y to 33K, and Y to K color toner images are superimposed on the same positions on the intermediate transfer belt 11 and primarily transferred onto the photosensitive drums 31Y to 31K. It is executed at different timings.
The toner images of the respective colors are sequentially transferred onto the intermediate transfer belt 11 by the electrostatic force acting on the primary transfer rollers 34Y to 34K to form a full-color toner image, and further move toward the secondary transfer position 46.

  On the other hand, the paper feed unit 4 includes a paper feed cassette 41 that stores the recording sheets S, a feed roller 42 that feeds the recording sheets S in the paper feed cassette 41 one by one onto the transport path 43, and a fed recording sheet S. Are provided with a timing roller pair 44 for taking the timing of feeding the toner to the secondary transfer position 46, and the recording sheet S is transferred from the paper feeding unit 4 to the secondary transfer position in accordance with the movement timing of the toner image on the intermediate transfer belt 11. The toner images on the intermediate transfer belt 11 are collectively transferred onto the recording sheet S by the action of the secondary transfer roller 45.

The recording sheet S that has passed the secondary transfer position 46 is conveyed to the fixing unit 5.
The fixing unit 5 is an electromagnetic induction heating type fixing device, and heats and melts the toner image (unfixed image) on the recording sheet S to fix it on the recording sheet S.
The recording sheet S on which the toner image is fixed is discharged onto a discharge tray 72 via a discharge roller pair 71.
<Configuration of fixing unit>
FIG. 2 is a partial cross-sectional perspective view showing the configuration of the fixing unit 5.

3A is a perspective plan view of the fixing unit 5 (drawn with the lid 175 omitted), and FIG. 3B is a sectional view taken along the line DD ′ of FIG. 3C. ) Is an enlarged view of a main part of FIG.
As shown in FIG. 3B, the fixing unit 5 includes a pressure roller 150, a pressure roller 160, a fixing belt 154, and an induction heating unit 170.

  The pressure roller 150 is loosely inserted into the fixing belt 154, and the pressure roller 150 and the pressure roller 160 are arranged in parallel. The pressure roller 160 is pressed by a biasing mechanism (not shown) via the fixing belt 154. By energizing the roller 150, a fixing nip is formed between the fixing belt 154 and the pressure roller 160, and the toner image formed on the recording sheet S when the recording sheet S passes through the fixing nip. T is melted and pressurized to be fixed.

Details of each part will be described below.
<Configuration of pressure roller>
As shown in FIG. 2, the pressure roller 160 includes a roller shaft 161, an elastic layer 162, and a release layer 163.
The roller shaft 161 is, for example, an aluminum shaft, and is rotationally driven by a drive mechanism (not shown).

The elastic layer 162 is a cylindrical elastic body made of silicone sponge rubber or the like.
The release layer 163 is a resin layer made of a fluorine resin such as PFA.
<Configuration of pressure roller>
The pressing roller 150 includes a roller shaft 152, a heat insulating elastic layer 153, and a guide plate 157.

The roller shaft 152 is an aluminum shaft, for example, and both ends thereof are supported by bearings (not shown).
The heat insulating elastic layer 153 is a sponge body of silicone rubber having high elasticity and high heat insulating properties, and is provided so as to cover a portion excluding both ends of the roller shaft 152.
The guide plate 157 is a hook-shaped member that abuts against the edge of the fixing belt 154 and regulates the position of the fixing belt 154 in the width direction (the axial direction of the roller shaft 152), and the other end portion of the roller shaft 152. Also attached to.
<Configuration of fixing belt>
FIG. 4 is a partial cross-sectional view showing a laminated structure of the fixing belt 154.

As shown in the figure, the fixing belt 154 is formed by laminating a metal heating layer 154c, an elastic layer 154b, and a release layer 154a from the inner peripheral surface side as shown in the figure.
The metal heat generating layer 154c is made of a Ni electroformed sleeve, and generates Joule heat when an induction current flows by an alternating magnetic flux generated by the induction heating unit 170.
The elastic layer 154b is made of, for example, silicone rubber, and the release layer 154a is made of a PFA resin tube or the like.

<Induction heating unit>
The induction heating unit 170 generates an alternating magnetic field toward the fixing belt 154, and as shown in FIG. 2, a coil bobbin 171, a side magnetic body core 172, an excitation coil 173, an arch magnetic body core 174, and a lid 175. Etc.
The exciting coil 173 is connected to a high-frequency inverter (not shown), and generates an alternating magnetic field by supplying high-frequency power of 10 to 100 [kHz] and 100 to 2000 [W].

  More specifically, as shown in FIG. 3C, the exciting coil 173 is formed of 115 litz wires 181 in which 115 strands (copper wire covered with enamel) are twisted. The surface covered with the thermal adhesive 182 is wound around a winding jig (not shown) having the same shape (oval shape) as the coil bobbin 171, and then the Ritz wire 181 is energized to generate Joule heat. By melting the fusing agent 182 temporarily, the shape is fixed by thermally fusing the adjacent litz wires 181 together.

The excitation coil 173 whose shape is fixed in this way is partially bonded to the coil bobbin 171 by an adhesive 183 applied to the holding surface 171a of the coil bobbin 171. Details will be described later.
The coil bobbin 171 is for holding the exciting coil 173 on the holding surface 171a and positioning the exciting coil 173 along the peripheral surface of the fixing belt 154, and has heat resistance and insulation. Manufactured by injection molding resin material.

As the resin material, it is more preferable to use a material such as a liquid crystal polymer that has little dimensional change due to temperature.
As shown in FIG. 3B, the holding surface 171a is curved along the circumferential direction of the outer surface of the fixing belt 154. The exciting coil 173 held along the holding surface 171a and the surface of the fixing belt 154 The distance between and is configured to be substantially the same in any part.

  As shown in FIG. 3C, the circumferential edges of the curved holding surface 171a of the coil bobbin 171 are each 1 in a direction away from the fixing belt 154 (hereinafter referred to as “outward”). A pair of flange portions 177 is erected, and a plurality of protrusions 178 are erected along the flange portion 177. Further, a central portion in the circumferential direction of the holding surface 171a is 1 A pair of vertical wall portions 176a and 176b are also erected outward.

The vertical wall portions 176a and 176b are connected at both longitudinal ends of the coil bobbin 171 (not shown), and constitute the central vertical wall portion 176 as a unit.
The central vertical wall 176 and the protrusion 178 are for positioning the exciting coil 173 with respect to the coil bobbin 171.
In order to place the exciting coil 173 on the holding surface 171a of the coil bobbin 171, when the central vertical wall 176 is inserted into the central hole 173a of the exciting coil 173, as shown in FIG. Since the inner surface of the coil and the outer edge of the exciting coil 173 are close to each other, the center vertical wall portion 176 and the protruding portion 178 are formed on the exciting coil 173 when the insertion is attempted to deviate from the normal position. It abuts against the inner edge and the outer edge to suppress the occurrence of the positional deviation.

The pair of side magnetic cores 172 are each made of a ferromagnetic material and are disposed along the inner wall of each flange portion 177 of the coil bobbin 171.
The arch magnetic core 174 is also made of a ferromagnetic material and is disposed so as to straddle the pair of side magnetic cores 172.
The lid portion 175 is made of an insulating material such as resin, and serves to cover the coil bobbin 171 in a state in which the side magnetic body core 172, the excitation coil 173, and the arch magnetic body core 174 are accommodated. The excitation coil 173 and the like are not touched.
(Adhesion structure between excitation coil and coil bobbin)
FIG. 5A is a plan view of the coil bobbin 171 and FIG. 5B is an enlarged cross-sectional view taken along line GG ′ of FIG.

As shown in FIG. 5A, the holding surface 171 a is provided so as to surround the central vertical wall portion 176.
Further, as shown in FIG. 5B, the surface of the holding surface 171a is formed with minute irregularities on the surface by blasting or the like, and the surface roughness is set large.
As the adhesive 183, one having heat resistance and having a predetermined elasticity even in a solidified state (hereinafter, also referred to as “elastic adhesive”) is used. Typically, a silicone-based adhesive is used. used.

As shown in FIG. 5A, the adhesive 183p before being solidified is applied in a zigzag shape with a single stroke on the holding surface 171a of the exciting coil 173 in the coil bobbin 171.
By the way, since the exciting coil 173 generates Joule heat by energization, the heat fusion agent is softened by the heat, and when an external force is applied to the exciting coil or the thermal expansion of the exciting coil itself occurs. The fused part is peeled off and the coil shape tends to collapse.

  Therefore, the adhesive 183p is applied so that the adhesive 183p crosses between the outer edge and the inner edge of the oval excitation coil 173 when the excitation coil 173 is placed on the holding surface 171a. Even if the separation of the heat-melting portions between the adjacent litz wires 181 occurs in a wide range, at least the litz wire 181 where the adhesive 183p crosses is fixed to the holding surface 171a. The collapse of the shape can be suppressed.

In the conventional induction heating unit, when the exciting coil 173 and the coil bobbin 171 are bonded, an adhesive is applied to the entire holding surface.
For this reason, the excitation coil has a larger coefficient of thermal expansion than the resin coil bobbin, and the induction heating unit 540 is heated by Joule heat generated by energization of the excitation coil or radiation heat from the metal heating layer that is induction heated. The difference between the amount of thermal expansion of the exciting coil and the amount of expansion of the coil bobbin increases mainly in the longitudinal direction, and a large thermal stress is generated between the two.

As a result, a force is generated to bend the coil bobbin in the direction opposite to the bonding surface of the exciting coil, and the plastic bobbin is deformed in a state where the coil bobbin is bent by receiving a thermal stress by repeating the fixing operation for a long time. It will be done.
Therefore, in the induction heating unit 170 in the present embodiment, the adhesive 183p before solidification is applied not partially on the entire holding surface 171a but partially (here, in a zigzag shape with a single stroke) as described above. .
FIG. 6A is an enlarged cross-sectional view of the bonded portion where the exciting coil 173 is mounted on the coil bobbin 171 to which the adhesive 183p is partially applied as described above, and the bonding is completed, and FIG. These are the figures explaining the relative position change in the both ends (end part 171b, 171c) of the exciting coil 173 and the coil bobbin 171 when the induction heating unit 170 is heated in Fig.6 (a).

When the induction heating unit 170 is not heated (at a room temperature of 25 ° C.), as shown in FIG. 6A, there is no positional deviation between both ends of the exciting coil 173 and the coil bobbin 171.
On the other hand, at the time of fixing, the induction heating unit 170 is also heated to around 180 ° C., and the exciting coil 173 tends to extend particularly in the longitudinal direction, but the adhesive 183 after solidification is as shown in FIG. Since it is elastically deformed, the stress on both adhesion surfaces is relaxed.

Here, as shown in FIG. 6A, the adhesive 183 is appropriately elastically deformed so that the coil bobbin 171 is not bent and the exciting coil 173 is not peeled when the induction heating unit 170 is heated. In addition, the hardness is set.
As the hardness of the adhesive 183 in the present embodiment, an adhesive of 25 ° or more and 50 ° or less is selected in the durometer A hardness measurement method.

  The advantage of applying the adhesive 183 in a zigzag manner with one stroke as described above is that the adhesive 183 is discharged from the tip of the nozzle while moving the nozzle of the dispenser device, and the adhesive is applied onto the holding surface 171a. When the method of applying 183 is employed, it is not necessary to interrupt the discharge of the adhesive 183 from the start point to the end point of the nozzle movement trajectory, and therefore the adhesive 183 can be applied efficiently. The manufacturing time can be reduced by shortening the coating time.

In the induction heating unit 170 according to the present embodiment, the bonding area is reduced as compared with the conventional case where bonding is performed on the entire holding surface 171a. The problem does not occur.
In this embodiment, in order to more reliably prevent peeling between the adhesive 183 and the coil bobbin 171, the surface roughness of the holding surface 171a is increased as described above to increase the adhesive strength.

In addition, as shown in FIG. 5A, the adhesive 183 has a ratio of the area to which the adhesive 183 per unit area is applied to the other portions (hereinafter referred to as “the end” 171b and 171c of the holding surface 171a). It is set to be larger than 171d).
Here, the ratio of the area where the adhesive 183 per unit area is applied to the end portions 171b and 171c is about 25%, and the area where the adhesive 183 per unit area is applied to the central portion 171d. The ratio is about 15%.

This is to further increase the adhesive strength at the end portions 171b and 171c where the excitation coil 173 is easily peeled off.
With the above configuration, it has been confirmed that even when the induction heating unit 170 is used for a long period of time, the peeling of the exciting coil 173 and the occurrence of bending of the coil bobbin 171 are suppressed as compared with the conventional case.

The inventor also confirmed the case where the elastic adhesive was applied to the entire holding surface 171a.
As a result, it has been found that the peeling of the exciting coil 173 and the bending of the coil bobbin 171 cannot be suppressed to a great extent.
This is considered to be due to the fact that, even if an elastic adhesive is used, if it is applied to the entire surface, its rigidity becomes strong and the thermal stress cannot be sufficiently absorbed.

<Modification>
The present invention is not limited to the embodiment as described above, and may be modified as follows.
(1) In the above embodiment, the adhesive 183 is applied in a zigzag shape with a single stroke on the holding surface 171a of the exciting coil 173 in the coil bobbin 171 as shown in FIG. However, it is not limited to this.

For example, as shown in FIG. 7A, the adhesive 183 may be applied in a stripe shape.
Even in such a case, in order to increase the adhesive strength of both end portions (end portions 171b, 171c) of the holding surface 171a where the excitation coil 173 is easily peeled off, the bonding area per unit area of these regions is It is desirable to make it larger than the central portion 171d.
At this time, when applying the adhesive 183 using the dispenser device, as shown in FIG. 7B, the nozzle for discharging the adhesive 183 is moved so as to follow the movement trajectory of the nozzle in the same figure. When coating is performed, the coating can be performed efficiently.

Alternatively, as shown in FIG. 8, an adhesive 283 may be applied along each of the inner edge and the outer edge of the holding surface 171a curved in accordance with the shape (oval shape) of the exciting coil 173 in plan view.
By doing in this way, even if the heat fusion part is peeled off between adjacent litz wires 181, only the inner edge and the outer edge of the exciting coil 173 are firmly fixed to the holding surface 171 a. Even if the litz wire 181 sandwiched between the inner edge and the outer edge is about to move, it is difficult for the litz wire 181 to move in the direction along the holding surface 171a, so that the collapse of the coil shape can be suppressed.

  Here, when an adhesive 283b is applied along the inner edge and an adhesive 283c is applied along the outer edge, both end portions (end portions 171b, 171c) of the holding surface 171a in FIG. The distance W3 between the adhesive 283b and the adhesive 283c is larger than the distance W4 between the adhesive 283b and the adhesive 283c at the central portion 171d, and the both end portions of the holding surface 171a have a smaller adhesion area per unit area. 3B, in fact, as shown in FIG. 3B, the holding surface 171a is curved, so only the interval W4 appears to be narrow, and the values of the interval W3 and the interval W4 substantially match, Both the end portions (end portions 171b and 171c) and the central portion 171d have the same bonding area per unit area.

The above is a configuration in which the adhesive is applied in a line shape, but the adhesive 383 may be applied in a dot shape as shown in FIG.
In the figure, the adhesive 383 is set so that the application area per unit at both end portions (end portions 171b and 171c) of the holding surface 171a is larger than the central portion 171d.

(2) In the above embodiment, the configuration in which the exciting coil 173 and the coil bobbin 171 are joined only by the adhesive 183 is exemplified. However, in addition to the configuration in which the exciting coil 173 and the coil bobbin 171 are bonded by the adhesive 183, You may have the structure which strengthens further joining.
In the following, a modified example to which such a configuration is added will be described. Since most of the configurations are the same as those of the induction heating unit 170 in the embodiment, in the configuration common to the induction heating unit 170, The same reference numerals are assigned, and the signs are changed only in the case of different configurations.

FIG. 10A is a diagram showing a modified example to which a configuration in which the joining between the exciting coil 173 and the coil bobbin 271 is strengthened, and FIG. 10B is a cross-sectional view taken along line EE ′ thereof.
Here, the coil bobbin 271 has a different sign because the heights of the vertical wall portions 276a and 276b provided at the center of the coil bobbin 171 and the shape of the projections 178 are different. Except for being added to, it is the same as induction heating unit 170 in the present embodiment.

In addition, the side magnetic body core 172, the arch magnetic body core 174, and the cover part 175 are abbreviate | omitted for convenience.
As shown in both drawings, the induction heating unit 270 includes an elastic member 190 that urges the entire exciting coil 173 toward the holding surface 271a of the coil bobbin 271.
The elastic member 190 is a rectangular net having stretchability made of heat-resistant resin fibers having a wire diameter of φ0.5 mm to φ1.0 mm.

The elastic member 190 covers the exciting coil 173 and is engaged with the coil bobbin 271 with its outer edge pulled in the radial direction.
More specifically, as shown in FIG. 10 (b), the outer edge 190 a of the elastic member 190 is hooked by a protrusion 278 having a plurality of hooks standing from the coil bobbin 271. Is done.

Further, since the elastic member 190 has a thin wire diameter of φ0.5 mm to φ1.0 mm as described above, there is no problem that the assembly workability is deteriorated by interference with other members.
Here, in order to apply a pressing force to the entire exciting coil 173, the height h3 of the vertical wall portions 276a and 276b provided at the center of the coil bobbin 271 is equal to the thickness t of the exciting coil 173. Or it is set slightly lower.

The above is a configuration in which a net is used as the elastic member 190 that biases the exciting coil 173 toward the holding surface 271a of the coil bobbin 271. However, a member other than the net may be used.
FIG. 11A is a plan view showing a configuration using a member other than the net as the elastic member 190, FIG. 11B is a sectional view taken along line FF ′, and FIG. ) Is a cross-sectional view taken along line JJ ′ of FIG.

In FIG. 11A, the lid 175 is omitted for convenience.
As shown in FIG. 11A, the induction heating unit 370 includes a long pressing member 210 and an elastic member 220 provided along the longitudinal direction of the exciting coil 173, and other configurations are as follows. This is the same as the induction heating unit 170 in the present embodiment.
As shown in FIG. 11B, the pressing member 210 has a lower surface shape along the upper surface side (convex surface side) shape of the excitation coil 173, and the lower surface side of the pressing member 210 is placed on the upper surface of the excitation coil 173. Is done.

The elastic members 220 are, for example, elastic silicone rubber sponge bodies, and four elastic members 220 are provided at substantially evenly distributed positions in the longitudinal direction of the pressing member 210 as shown in FIG.
Further, as shown in FIGS. 11B and 11C, the elastic member 220 is sandwiched between the inner wall of the lid 175 and the upper surface of the pressing member 210, and is in a state where elastic deformation occurs. The specific force of the exciting coil 173 is pressed toward the holding surface 171a of the coil bobbin 171 through the pressing member 210 by the restoring force.

As a result, both end portions (end portions 171b and 171c) where the excitation coil 173 is likely to be peeled off and the central portion 171d can be firmly pressed down.
Further, in order to save the labor of providing four at dispersed positions like the elastic member 220, a sheet 222 having heat resistance and elasticity having the same shape as that of the upper surface of the exciting coil 173 is shown in FIG. As shown in FIG. 5, it may be interposed between the pressing member 210 and the exciting coil 173.

At this time, in order to elastically deform the sheet 222, that is, to apply a preload, it is necessary to provide a contact portion 275a for projecting a part of the inner wall of the lid portion 275 to contact the pressing member 210.
Alternatively, as shown in FIG. 12B, the pressing member 210 that is rigid and does not cause elastic deformation is replaced with a pressing member 214 having heat resistance and elasticity such as silicone rubber, and the sheet 222 is eliminated. In the state where the contact portion 275a is in contact with the pressing member 276, the pressing member 214 itself may be in an elastically deformed state, that is, in a state where a preload is applied.

(3) In the above embodiment, the plurality of protrusions 178 are provided along the outer periphery of the holding surface 171a of the coil bobbin 171. However, the present invention is not limited to this configuration.
For example, instead of the plurality of projecting portions 178, one vertical wall portion formed by connecting the plurality of projecting portions 178 to each other (hereinafter referred to as "annular vertical wall portion") may be provided. Even with such an annular vertical wall portion, the excitation coil 173 can be positioned in the same manner as the plurality of protrusions 178 described above.

  The central vertical wall portion 176 also contributes to the positioning of the excitation coil 173, and the central vertical wall portion 176 and the annular ring vertical wall portion abut on the inner edge and the outer edge of the excitation coil 173, respectively. The position of 173 is regulated and the positioning of the exciting coil 173 is performed. As a structure to be brought into contact with the inner edge and the outer edge of the exciting coil 173 in this way, the coil bobbin 171 is recessed according to the shape of the exciting coil 173. It is good also as a structure which provides a recessed part and engages the exciting coil 173 in this recessed part, and controls a position.

(4) In the above embodiment, the pressing roller 150 is loosely inserted into the fixing belt 154. However, the present invention is not limited to this.
For example, a pressing member that is pressed through the fixing belt 154 by the pressure roller 160 while guiding the fixing belt 154 in the rotating direction without rotating as the fixing belt 154 rotates is fixed. The structure inserted loosely inside the circulation route of 154 may be sufficient.

Alternatively, instead of providing the fixing belt 154, a metal heating layer 154c may be provided on the outer surface of the heat insulating elastic layer 153 of the pressure roller 150.
(5) In the above embodiment, an example in which the image forming apparatus according to the present invention is applied to a tandem color digital printer has been described. However, the present invention is not limited to this, and recording is performed by heating a fixing belt by induction heating. The present invention can be applied to all fixing devices and image forming apparatuses that include an induction heating unit that thermally fixes an unfixed image on a sheet.

  Further, the contents of the above embodiment and the above modification may be combined.

  The present invention can be widely applied to an induction heating unit, a fixing device, and an image forming apparatus that heat-fix an unfixed image on a recording sheet by heating a fixing belt by induction heating.

DESCRIPTION OF SYMBOLS 1 Printer 3 Image process part 30Y, 30M, 30C, 30K Image creation part 4 Paper feed part 5, 105 Fixing part 10 Optical part 11 Intermediate transfer belt 12 Drive roller 13 Driven roller 31 Photosensitive drum 32 Charger 33 Developer 34 Primary Transfer roller 35 Cleaner 41 Paper feed cassette 42 Roller 43 Conveying path 44 Timing roller pair 45 Secondary transfer roller 46 Secondary transfer position 60 Control unit 71 Discharge roller pair 72 Discharge tray 150 Press roller 152 Roller shaft 153 Heat insulation elastic layer 154 Fixing belt 154a Release layer 154b Elastic layer 154c Metal heating layer 156 Release layer 160 Pressure roller 161 Roller shaft 162 Elastic layer 163 Release layer 170 Induction heating unit 171 Coil bobbin 171a Holding surface 171b End portion 171d Central portion 172 Side magnetic body A 173 Excitation coil 174 Arch magnetic body core 175 Lid 176 Center vertical wall 176a, 176b Vertical wall 177 Flange 178 Protrusion 181 Litz wire 182 Thermal adhesive 183, 183p, 283, 283b, 283c, 383 Adhesive 190 Elastic member 190a Outer edge part 210, 214 Pressing member 220 Elastic member 222 Sheet 270, 370 Induction heating unit 271 Coil bobbin 275 Lid part 275a Abutting part 276 Pressing member 276a, 276b Vertical wall part 278 Projection part

Claims (21)

An induction heating unit in a fixing device that heats a conductive heat generating rotator by electromagnetic induction to thermally fix a toner image on a recording sheet,
A coil bobbin disposed in the longitudinal direction along the axial direction of the heat generating rotating body;
An exciting coil formed by winding a conductive wire and adhered to the coil holding surface of the coil bobbin with an adhesive;
With
The induction heating unit is characterized in that the adhesive has elasticity in a solidified state and is partially applied to a predetermined region of the coil holding surface. The induction heating unit according to claim 1, wherein the predetermined region includes at least a region corresponding to both ends of the coil in the longitudinal direction.   The application area per unit area of the adhesive on the coil holding surface of the adhesive is such that the region corresponding to both ends in the longitudinal direction of the coil is equal to or greater than the other regions. Item 3. The induction heating unit according to Item 1 or 2.   The induction heating unit according to any one of claims 1 to 3, wherein the adhesive is applied in a line shape to the coil holding surface.   The induction heating according to any one of claims 1 to 4, wherein the adhesive is applied to the coil holding surface so that its application shape is a zigzag shape or a meandering shape in a single stroke state. unit. The induction heating unit according to any one of claims 1 to 4, wherein the adhesive is applied in a stripe shape. The exciting coil is wound in an oval shape,
The adhesive is
A first path provided along the inner periphery of the exciting coil;
The induction heating unit according to claim 3, wherein the induction heating unit is applied along a second path provided along the outer periphery of the excitation coil.   The induction heating unit according to claim 3, wherein the coil holding surface of the coil bobbin is provided with irregularities to increase the contact area with the adhesive.   The induction heating unit according to claim 8, wherein the unevenness is formed by performing a blasting process on the coil holding surface.   The induction heating unit according to claim 2, wherein the adhesive is applied in a dot shape.   The induction heating unit according to any one of claims 1 to 10, wherein the adhesive is a silicone adhesive.   The induction heating unit according to any one of claims 1 to 11, further comprising pressing means for pressing the entire exciting coil or a specific portion toward a coil holding surface of the coil bobbin. The pressing means is a net having elasticity and heat resistance attached to a coil bobbin so as to cover the exciting coil in a state having tension.
The induction heating unit according to claim 12, wherein the net is configured to press the exciting coil toward the coil holding surface. The pressing means is
A pressing member provided along the shape of the surface of the exciting coil opposite to the surface attached to the coil holding surface;
The induction heating unit according to claim 12, further comprising: an urging unit that urges the excitation coil in the direction of the coil holding surface via the pressing member. A lid member mounted so as to cover the excitation coil;
The induction heating unit according to claim 14, wherein the urging unit is an elastic member interposed in a compressed state between the lid member and the pressing member. The pressing means is
A pressing member provided along the shape of the surface of the exciting coil opposite to the surface attached to the coil holding surface;
It consists of a sheet-like elastic member inserted between the pressing member and the exciting coil,
When the pressing member is attached to the coil bobbin in a state where the sheet-like elastic member is compressed, the exciting coil is directly urged toward the coil holding surface by the elastic force of the elastic member. The induction heating unit according to claim 12, wherein the induction heating unit is provided.   The induction heating unit according to claim 1, wherein the coil bobbin has a positioning portion that contacts an edge of the excitation coil to position the excitation coil.   The positioning portion is a recess provided on a coil holding surface of the coil bobbin along the shape of the excitation coil, and the excitation coil is positioned by fitting the excitation coil into the recess. The induction heating unit according to claim 17.   The positioning portion is a protrusion erected on a coil holding surface of the coil bobbin, and the excitation coil is positioned when the protrusion abuts against an edge of the excitation coil. The induction heating unit according to 17. A fixing device comprising the induction heating unit according to claim 1.   An image forming apparatus comprising the fixing device according to claim 20.

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