Patent Description:
A laminated heater having a planar resistive heat generator is known as a heater used for a drying device to dry ink on a sheet or a fixing device to fix toner on the sheet by heat in an image forming apparatus such as a printer and a copier.

The laminated heater generates heat when power is supplied to the resistive heat generator. Therefore, the laminated heater includes an electrode to which a connector is electrically connected to supply power from the power supply.

For example, <CIT> discloses a configuration of the connector connected to the electrode of the laminated heater, in which the laminated heater is sandwiched from the front side and the back side thereof, and a contact terminal of the connector presses against the electrode of the laminated heater.

The laminated heater has an issue that variation in contact pressure of the contact terminal pressed against the electrode causes an application of the contact pressure stronger than necessary contact pressure to the electrode, or conversely, shortage of the contact pressure.

As a solution to such the issue, <CIT> proposes a configuration in which the contact terminal is movable relative to the housing of the connector.

<CIT>, <CIT>, <CIT>, <CIT> and <CIT> disclose heating devices.

It is a general object of the present disclosure to provide an improved and useful heater in which the above-mentioned problems are eliminated. In order to achieve the above-mentioned object, there is provided a heater according to claim <NUM>. Advantageous embodiments are defined by the dependent claims. Advantageously, the heater includes an electrode, a heat generator, and a plate having a portion corresponding to the electrode thinner than a portion corresponding to the heat generator.

The present disclosure enables to reduce the variation in the contact pressure of the contact terminal with respect to the electrode and set the contact pressure to an appropriate value, that is, within an appropriate range.

The aforementioned and other aspects, features, and advantages of the present disclosure would be better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:.

Although the embodiments are described with technical limitations with reference to the attached drawings, such description is not intended to limit the scope of the disclosure and all of the components or elements described in the embodiments of this disclosure are not necessarily indispensable.

In the drawings illustrating the following embodiments, the same reference numbers are allocated to elements having the same function or shape and redundant descriptions thereof are omitted below.

<FIG> is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present disclosure.

The image forming apparatus <NUM> illustrated in <FIG> includes four image forming units 1Y, <NUM>, 1C, and 1Bk detachably attached to an apparatus body thereof. The image forming units 1Y, <NUM>, 1C, and 1Bk have the same configuration except for containing different color developers, i.e., yellow (Y), magenta (M), cyan (C), and black (Bk) toners, respectively, corresponding to decomposed color separation components of full-color images. Specifically, each of the image forming units 1Y, <NUM>, 1C, and 1Bk includes: a photoconductor <NUM> in a drum-like shape as an image bearer; a charger <NUM> to charge a surface of the photoconductor <NUM>; a developing device <NUM> configured to form a toner image by supplying toner, as a developer, to a surface of the photoconductor <NUM>; and a cleaner <NUM> to clean the surface of the photoconductor <NUM>.

The image forming apparatus <NUM> further includes an exposure device <NUM> to expose the surface of each photoconductor <NUM> to form an electrostatic latent image, a sheet feeder <NUM> to supply a sheet P as a recording medium, a transfer device <NUM> to transfer the toner image formed on the each photoconductor <NUM> onto the sheet P, a fixing device <NUM> to fix the transferred toner image onto the sheet P, and an output device <NUM> to eject the sheet P outside the image forming apparatus <NUM>.

The transfer device <NUM> includes: an intermediate transfer belt <NUM> in the form of an endless belt stretched taut with multiple rollers, as an intermediate transferor; four primary transfer rollers <NUM> each as a primary transferor to transfer the toner image formed on each photoconductor <NUM> onto the intermediate transfer belt <NUM>; and a secondary transfer roller <NUM> as a secondary transferor to transfer the toner image transferred onto the intermediate transfer belt <NUM> onto the sheet P. The primary transfer rollers <NUM> are in contact with the respective photoconductors <NUM> via the intermediate transfer belt <NUM>. Therefore, the intermediate transfer belt <NUM> is in contact with the respective photoconductors <NUM>, thus forming primary transfer nips therebetween. The secondary transfer roller <NUM> contacts, via the intermediate transfer belt <NUM>, one of the plurality of rollers around which the intermediate transfer belt <NUM> is stretched. Thus, the secondary transfer nip is formed between the secondary transfer roller <NUM> and the intermediate transfer belt <NUM>.

In the image forming apparatus <NUM>, a sheet conveyance path <NUM> is formed through which the sheet P fed from the sheet feeder <NUM> is conveyed. A timing roller pair <NUM> is disposed on the sheet conveyance path <NUM> on the way from the sheet feeder <NUM> to the secondary transfer nip (the secondary transfer roller <NUM>).

Next, a description is given of a print operation of the image forming apparatus <NUM> with reference to <FIG>.

As a print operation start is instructed, in each of the image forming units 1Y, <NUM>, 1C, and 1Bk, the photoconductors <NUM> are each driven to rotate clockwise in <FIG> and the surfaces thereof are uniformly charged to a high potential by the respective chargers <NUM>. Subsequently, according to either image data of a document scanned by a scanner or print data instructed from a terminal, the exposure device <NUM> exposes the surface of the photoconductor <NUM>. Thus, the potential of the exposed portion decreases, and an electrostatic latent image is formed. The developing device <NUM> supplies toner to the electrostatic latent image, thereby developing the latent image into the toner image on each of the photoconductors <NUM>.

The toner image on each of the photoconductors <NUM> reaches the primary transfer nip at each of the primary transfer rollers <NUM> in accordance with rotation of each of the photoconductors <NUM> and is sequentially transferred and superimposed onto the intermediate transfer belt <NUM> that is driven to rotate counterclockwise in <FIG>. In accordance with rotation of the intermediate transfer belt <NUM>, the toner image transferred onto the intermediate transfer belt <NUM> reaches the secondary transfer nip at the secondary transfer roller <NUM> and is transferred onto the conveyed sheet P at the secondary transfer nip. The sheet P is fed from the sheet feeder <NUM>. The timing roller pair <NUM> temporarily stops the sheet P fed from the sheet feeder <NUM> and conveys the sheet P to the secondary transfer nip, timed to coincide with the toner image on the intermediate transfer belt <NUM>. Thus, a full-color toner image is formed on the sheet P. After the toner image is transferred from each of the photoconductors <NUM> onto the intermediate transfer belt <NUM>, each of cleaners <NUM> removes residual toner on each of the photoconductors <NUM>.

The sheet P transferred the toner image is conveyed to the fixing device <NUM> that fixes the toner image on the sheet P. Subsequently, the output device <NUM> ejects the sheet P outside the image forming apparatus <NUM>, and a series of print operations are completed.

Next, a configuration of the fixing device <NUM> is described.

As illustrated in <FIG>, the fixing device <NUM> according to the present embodiment includes an endless fixing belt <NUM> as a fixing rotator, a pressure roller <NUM> as an opposed rotator to contact an outer circumferential surface of the fixing belt <NUM> and form a nip N, and a heating device <NUM> to heat the fixing belt <NUM>. The heating device <NUM> includes a laminated heater <NUM> as a heater, a heater holder <NUM> as a holder to hold the heater <NUM>, and a stay <NUM> as a supporter to support the heater holder <NUM>.

The fixing belt <NUM> includes, for example, a tubular base made of polyimide (PI), the tubular base having an outer diameter of <NUM> and a thickness of from <NUM> to <NUM>. On the outermost layer of the fixing belt <NUM>, a release layer made of a fluorine-based resin, such as a perfluoroalkoxy alkane (PFA) or polytetrafluoroethylene (PTFE), having a thickness of from <NUM> to <NUM>, is formed in order to improve durability and ensure releasability. An elastic layer made of rubber having a thickness of from <NUM> to <NUM> may be provided between the base and the release layer. The base of the fixing belt <NUM> is not limited to polyimide, and thus may be made of heat-resistant resin, such as polyetheretherketone (PEEK), or a metal, such as nickel (Ni) or stainless steel (SUS). The inner circumferential surface of the fixing belt <NUM> may be coated with polyimide or polytetrafluoroethylene (PTFE) as a slide layer.

The pressure roller <NUM> having, for example, an outer diameter of <NUM>, includes a bar 21a made of solid iron, an elastic layer 21b on the surface of the bar 21a, and a release layer 21c formed on the outside of the elastic layer 21b. The elastic layer 21b is made of silicone rubber and has, for example, a thickness of <NUM>. Preferably, the release layer 21c is formed by a fluororesin layer having, for example, a thickness of approximately <NUM> on the surface of the elastic layer 21b to improve releasability.

The heater <NUM> extends in a longitudinal direction thereof parallel to a width direction of the fixing belt <NUM>. The heater <NUM> includes a heat insulation layer <NUM>, a base layer <NUM>, a first insulation layer <NUM>, a conductor layer <NUM> that includes a heat generator <NUM>, and a second insulation layer <NUM>, all of which are layered, in the order just given, onto and from the heater holder <NUM> toward the fixing belt <NUM>, that is, the nip N.

The heater holder <NUM> and the stay <NUM> are disposed inside the inner circumferential surface of the fixing belt <NUM>. The stay <NUM> is configured by a channeled metallic member, and both side plates of the fixing device <NUM> support respective end portions of the stay <NUM>. Supporting the heater holder <NUM> and the heater <NUM> held by the heater holder <NUM> by the stay <NUM> causes the heater <NUM> to be subjected to a pressing force of the pressure roller <NUM> while the pressure roller <NUM> presses the fixing belt <NUM> and forms the nip N stably.

The heater holder <NUM> is preferably made of heat-resistant material because heat from the heater <NUM> causes the heater holder <NUM> get hot. The heater holder <NUM> made of heat-resistant resin having low thermal conduction, such as a liquid crystal polymer (LCP), reduces heat transfer from the heater <NUM> to the heater holder <NUM> and provides efficient heating of the fixing belt <NUM>.

A biasing member such as a spring presses the pressure roller <NUM> against the fixing belt <NUM>. As a result, the pressure roller <NUM> is pressed against the heater <NUM> via the fixing belt <NUM> to form the nip N between the fixing belt <NUM> and the pressure roller <NUM>. A driver drives and rotates the pressure roller <NUM> in a direction of an arrow illustrated in <FIG>, and this rotation of the pressure roller <NUM> rotates the fixing belt <NUM>.

When the print operation starts, the pressure roller <NUM> is driven to rotate, and the fixing belt <NUM> starts to be rotated. The heater <NUM> is supplied with power, heating the fixing belt <NUM>. When the temperature of the fixing belt <NUM> reaches a predetermined target temperature called a fixing temperature, as illustrated in <FIG>, the sheet P bearing an unfixed toner image is conveyed to the nip N between the fixing belt <NUM> and the pressure roller <NUM>, and the unfixed toner image is heated and pressed on to the sheet P and fixed thereon.

<FIG> is a plan view of the heater <NUM> as viewed from the front side, and <FIG> is an exploded perspective view of the heater <NUM>. In the following description according to the present embodiment, the fixing belt <NUM> side, that is, the nip N side with respect to the heater <NUM> is referred to as "front side", and the heater holder <NUM> side is referred to as "back side".

As illustrated in <FIG>, the heater <NUM> according to the present embodiment is the heater including a plurality of layers, electrodes, and the heat generator connected to the electrodes. The plurality of layers included in the heater <NUM> are integrally formed. A method to form the layers integrally is, for example, a method coating the base layer <NUM>. In the present embodiment, examples of the plurality of layers included in the heater <NUM> are as follows. The heater <NUM> according to the present embodiment includes the planar base layer <NUM>, the first insulation layer <NUM> disposed on the front side of the base layer <NUM>, the conductor layer <NUM> disposed on the front side of the first insulation layer <NUM>, the second insulation layer <NUM> that covers the front side of the conductor layer <NUM>, and the heat insulation layer <NUM> disposed on the back side of the base layer <NUM> and is configured by stacking the plurality of these layers. The conductor layer <NUM> includes a pair of heat generators <NUM> formed of the laminated heaters, a pair of electrodes <NUM> disposed on one end in the longitudinal direction of each heat generator <NUM>, and a plurality of power supply lines <NUM> connecting the electrodes <NUM> and the heat generators <NUM> to each other. In addition, as illustrated in <FIG>, at least one part of each electrode <NUM> in the conductor layer <NUM> is exposed without being covered by the second insulation layer <NUM> to ensure connection with a connector described later.

The heat generator <NUM> may be made, for example, by coating on the base layer <NUM> with paste in which silver palladium (AgPd) and glass powder are compounded, by screen printing, after that, by baking the base layer <NUM>. The material of the heat generator <NUM> may include a resistance material, such as silver alloy (AgPt) or ruthenium oxide (RuO2), other than the above material. In the present embodiment, the pair of heat generators <NUM> extend in the longitudinal direction of the base layer <NUM> in parallel with each other. Right ends of the heat generators <NUM> in <FIG>, that is, ends of heat generators <NUM> in one side are electrically connected to each other through the power supply line <NUM>, and left ends of the heat generators <NUM> in <FIG>, that is, ends of heat generators <NUM> in the other side are electrically connected to the electrodes <NUM> through the different power supply line <NUM>. The power supply lines <NUM> are made of a conductor having a resistance value smaller than that of the heat generators <NUM>. Silver (Ag), silver palladium (AgPd) or the like may be used as a material of the power supply line <NUM> or the electrode <NUM>, and screen-printing such a material forms the power supply line <NUM> or the electrode <NUM>.

Although the heat generator <NUM> is disposed on the front side of the base layer <NUM> in the present embodiment, alternatively, the heat generator <NUM> may be disposed on the back side of the base layer <NUM>. In that case, since the heat of the heat generator <NUM> is transmitted to the fixing belt <NUM> through the base layer <NUM>, it is preferable that the base layer <NUM> be made of a material with high thermal conductivity such as aluminum nitride. Making the base layer <NUM> with a material having a high thermal conductivity enables to sufficiently heat the fixing belt <NUM> even if the heat generator <NUM> is disposed on the back side of the base layer <NUM>. Even when the base layer <NUM> is made of aluminum nitride, coating the materials of the layers other than the base layer <NUM> enables integrally forming the layers.

The base layer <NUM> is made of a metal material such as stainless steel (SUS), iron, or aluminum. Or, the base layer <NUM> may be made of ceramic, glass, etc. other than the metal material. The first insulation layer <NUM>, the second insulation layer <NUM>, and the heat insulation layer <NUM> are made of material having electrical insulation, high thermal conductivity, and heat resistance. In particular, materials having high insulating properties and heat resistance are preferable. Specifically, examples of these materials include heat-resistant resins such as glass, ceramic, and polyimide (PI). Increasing a thickness of each of the first insulation layer <NUM> and the second insulation layer <NUM> improves the electrical insulation but decreases thermal conductivity from the heat generator <NUM> to the fixing belt <NUM> and increase the cost. Therefore, the thickness of the first insulation layer <NUM> and the second insulation layer <NUM> is preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>. In the present embodiment, in order to increase the thermal conductivity, each of the first insulation layer <NUM> and the second insulation layer <NUM> is made of glass with a thickness of <NUM> to which a ceramic filler is added. Since the heat insulation layer <NUM> is required to have heat resistance and heat insulation, the heat insulation layer <NUM> is made of glass, ceramics, or heat resistant resin such as polyimide. Increasing a thickness of the heat insulation layer <NUM> improves heat insulation but increases the cost. Therefore, the thickness of the heat insulation layer <NUM> is preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>. In the present embodiment, in order to improve the heat insulation, the heat insulation layer <NUM> is made of glass with a thickness of <NUM>.

<FIG> is a perspective view illustrating the connector <NUM> coupled to the heater <NUM>. The heating device <NUM> according to the present embodiment includes the connector <NUM> to supply power to the heat generator <NUM> of the heater <NUM>. As illustrated in <FIG>, the connector <NUM> includes a housing <NUM> made of resin and a contact terminal <NUM> including a flat spring fixed to the housing <NUM>. The contact terminal <NUM> has a pair of contact portions 72a to contact the respective electrodes <NUM> of the heater <NUM>. In addition, a power supply harness <NUM> is coupled to the connector <NUM>.

As illustrated in <FIG>, the connector <NUM> is attached so as to sandwich the heater <NUM> and the heater holder <NUM> from the front side and the back side together. Thus, the contact portions 72a of the contact terminal <NUM> elastically contact and press against the electrodes <NUM> of the heater <NUM>, and the heat generator <NUM> is electrically connected to the power supply provided in the image forming apparatus via the connector <NUM> and can receive power from the power supply.

In the configuration in which the contact terminal <NUM> is pressed against the electrode <NUM> and coupled to the electrode <NUM>, as described in the present embodiment, any variation in the thickness (that is, a length in a lamination direction) of the heater <NUM> due to the combined tolerances of layers in the heater <NUM> changes a contact position between the contact terminal <NUM> and the electrode <NUM> of the heater <NUM> in the thickness direction. As a result, the contact pressure at the contact terminal <NUM> with respect to the electrode <NUM> also varies. Therefore, since an increase of the variation in a thickness of the heater <NUM> results in an increase in the contact pressure of the contact terminal <NUM>, the increase of the variation in the thickness of the heater <NUM> complicates control of the contact pressure to an appropriate value (within an appropriate range). If the contact pressure of the contact terminal <NUM> falls below the appropriate range, shortage of the contact pressure hinders maintaining electrical continuity, and an adequate electric power supply to the heater <NUM> is not ensured. In contrast, if the contact pressure of the contact terminal <NUM> exceeds an appropriate range, the contact terminal <NUM> and the electrode <NUM> of the heater <NUM> will wear when the heater <NUM> moves minutely due to vibration at the time of driving and power supply to the heater <NUM> becomes irregular. The heater moves slightly because the heater expands and contracts in the longitudinal direction of the heater due to heat and vibrates when the fixing belt vibrates due to acceleration and deceleration when the gear does not mesh properly with the pressure roller. In addition, the heater and the heater holder move slightly because sliding friction works the heater and the heater holder when the fixing belt slides on the heater and the heater holder.

A detailed description is given of the configuration of the heating device according to the present embodiment as follows. In the configuration according to the present embodiment, the following measures are taken to prevent above-described contact pressure defects (insufficient contact pressure or excessive contact pressure) of the contact terminal <NUM> caused by the variation in the thickness of the heater <NUM>.

<FIG> is a perspective view illustrating the heater <NUM> and the heater holder <NUM> according to the present embodiment. <FIG> is a bottom view illustrating the heater <NUM> viewed from a back side.

As illustrated in <FIG>, the heater <NUM> in the present embodiment has a rectangular hole 40a formed in the heat insulation layer <NUM> disposed on the back side of the heater <NUM>, that is, the side opposite to the side on which the conductor layer <NUM> is disposed. In other words, the heat insulation layer <NUM> is disposed in the opposite side with respect to a surface on which the electrode is disposed. The hole 40a is disposed at a position corresponding to the electrodes <NUM> disposed on the front side of the base layer <NUM>. That is, the heat insulation layer <NUM> is disposed on the back side of the base layer except for the back-side portion of the base layer <NUM> corresponding to the electrodes <NUM>, and a surface on the back-side portion of the base layer <NUM> corresponding to the electrode <NUM> is exposed. In other words, the heat insulation layer <NUM> has a plurality of portions around the hole 40a, and has a gap formed by the hole 40a between the plurality of portions.

On the other hand, the heater holder <NUM> includes a protrusion 23f in a recessed portion <NUM> of the heater holder <NUM> in which the heater <NUM> is accommodated. The recessed portion <NUM> has a bottom portion 23a formed in a rectangular shape substantially the same size as the heater <NUM>, and four side surface portions 23b, 23c, 23d, and 23e provided on each side (four sides) of the bottom portion 23a. In the recessed portion <NUM>, the protrusion 23f is provided in the position corresponding to the hole 40a formed in the heat insulation layer <NUM> so that the protrusion 23f protrudes from the bottom portion 23a.

<FIG> is a longitudinal cross-sectional view illustrating the heater <NUM> held by the heater holder <NUM>, and <FIG> is a cross-sectional view of the heater held by the heater holder along a line A-A of <FIG>.

As illustrated in <FIG>, when the heater <NUM> is accommodated and held in the recessed portion <NUM> of the heater holder <NUM>, the protrusion 23f of the heater holder <NUM> is inserted into the hole 40a of the heat insulation layer <NUM>, and a tip of the protrusion 23f is in contact with the back surface of the base layer <NUM>. As described above, the tip of the protrusion 23f contacts the back surface of the base layer <NUM>, and the protrusion 23f supports the base layer <NUM>. The protrusion 23f of the heater holder <NUM> is a contact portion that contacts the base layer <NUM>, but there is a slight gap between the bottom portion 23a of the heater holder <NUM> and the heat insulation layer <NUM>, and the bottom portion 23a is a portion not in contact with the back surface of the heater <NUM>. That is, in the present embodiment, the heat insulation layer <NUM> is removed and the hole 40a is provided in at least one part of the portion on which the contact portion of the heater holder <NUM>, that is, the protrusion 23f, contacts the back surface of the heater <NUM>.

<FIG> is a cross-sectional view illustrating the heater <NUM> held by the heater holder <NUM> and connected to the connector <NUM>.

As illustrated in <FIG>, when the connector <NUM> is attached, the heater <NUM> and the heater holder <NUM> are sandwiched from the front side and the back side together and held by the contact terminal <NUM>. In addition, in this state, the pair of contact portions 72a of the contact terminal <NUM> is pressed against the electrodes <NUM> of the heater <NUM>.

As described above, the variation in the thickness of the heater <NUM> at the contact portions 72a on which the contact terminal <NUM> is pressed against the electrodes <NUM> varies the contact pressure of the contact terminal <NUM> on the electrode <NUM>. Such variation in the thickness of the heater <NUM> tends to increase as the number of layers in the heater <NUM> increases. Conversely, decreasing the number of layers in the heater <NUM> can reduce the variation in the thickness of the heater <NUM>.

Focusing on such a point, as illustrated in <FIG>, the heater <NUM> in the present embodiment omits the heat insulation layer <NUM> on the back side of the base layer <NUM> corresponding to the electrodes <NUM>, and the number of layers in the heater <NUM> is reduced at the contact points between the electrodes <NUM> and the contact terminals <NUM>. This can reduce the variation in the thickness of the heater <NUM> at the contact points between the electrodes <NUM> and the contact terminals <NUM> compared with the heater including the heat insulation layer <NUM> disposed on a portion corresponding to the electrodes <NUM> as illustrated in <FIG> because the number of layers in the heater <NUM> on the portion corresponding to the electrodes <NUM> is small, and, therefore, the combined tolerances of the layers in the heater decreases. As a result, since the variation in the contact pressure of the contact terminals <NUM> is reduced, and since the contact pressure can be easily managed and prevented from being insufficient or excessive, the contact pressure can be set to the appropriate value (that is, within the appropriate range).

As described above, in the present embodiment, since the heat insulation layer <NUM> is omitted in a portion corresponding to the electrode <NUM>, as illustrated in <FIG>, a total thickness T2 in the lamination direction from a front side surface of the conductor layer <NUM> at the portion corresponding to the electrode <NUM> to a back side surface of the heater <NUM> that is the back side surface of the base layer <NUM> in the example illustrated in <FIG> is thinner than a total thickness T1 in the lamination direction from a front side surface of the conductor layer <NUM> at a portion corresponding to the heat generator <NUM> to the back side surface of the heater <NUM> that is a back side surface of the heat insulation layer <NUM> in the example illustrated in <FIG> by the thickness of the heat insulation layer <NUM>. In other words, the total thickness in the lamination direction of the portion including the layers in the heater <NUM> and are layered from the conductor layer <NUM> toward the base layer <NUM> is thinner at the portion corresponding the electrode <NUM> (T1) than at the portion corresponding to the heat generator <NUM> (T2). Generally, the variation in thickness tends to increase as the thickness of a member increases. Accordingly, as the heat insulation layer <NUM> becomes thicker, the effect of reducing the variation in heater thickness by partially omitting the heat insulation layer <NUM> becomes greater. Therefore, the thickness of the heat insulation layer <NUM> is desirably, for example, <NUM> or more. From the same viewpoint, the thickness of the heat insulation layer <NUM> is preferably <NUM> or more and more preferably <NUM> or more. In the laminated heater used in the fixing device, since an upper limit of the thickness of the heat insulation layer <NUM> is generally <NUM> or less, the most preferable range of the thickness of the heat insulation layer <NUM> is from <NUM> to <NUM>. Further, in the present embodiment, since the thickness of the heat insulation layer <NUM> corresponds to the difference between the total thickness T1 at the portion corresponding to the heat generator <NUM> and the total thickness T2 at the portion corresponding to the electrode <NUM>, in other words, the difference between these layer thicknesses becomes more preferable as the difference becomes <NUM> or more, <NUM> or more, and <NUM> or more, and the most preferable range is <NUM> or more and <NUM> or less.

In the present embodiment, since the heat insulation layer <NUM> is not disposed at the portion corresponding to the electrode <NUM>, the protrusion 23f is disposed on the heater holder <NUM> to support the base layer <NUM> from the back side at the portion corresponding to the electrode <NUM>. As described above, since the protrusion 23f disposed on the heater holder <NUM> supports the back side of the base layer <NUM>, the bending of the heater <NUM> decreases, and the contact pressure of the contact terminal <NUM> with respect to the electrode <NUM> becomes stable. In addition, decrease of the bending of the heater <NUM> can prevent damage to the heater <NUM> due to the bending.

Based on the above described function of the protrusion 23f, the protrusion 23f is preferably disposed at a position on which the contact pressure from the contact terminal <NUM> to the electrode <NUM> can be effectively received. Specifically, as illustrated in <FIG>, the protrusion 23f is preferably disposed at a position corresponding to at least the contact position C between the contact terminal <NUM> and the electrode <NUM> in a planar view. Disposing the protrusion 23f at such a position enables the protrusion 23f to effectively receive the contact pressure from the contact terminal <NUM>, stabilizes the contact pressure, and improves the certainty of preventing breakage of the heater <NUM>.

A height of the protrusion 23f (that is, a protrusion amount) is preferably set to be the same as the thickness of the heat insulation layer <NUM> so that the heater <NUM> can be reliably supported without bending. However, in practice, it is difficult to completely avoid errors in the thickness of the heater holder <NUM> and the heat insulation layer <NUM>. If the height of the protrusion 23f becomes larger than the thickness of the heat insulation layer <NUM>, the surface on the back side of the heater <NUM>, that is, the heat insulation layer <NUM> separates from the heater holder <NUM> as illustrated in <FIG>. In this case, since application of a pressing force F of the pressure roller to the heater <NUM> causes a bending of the heater <NUM>, the bending of the heater <NUM> may break the heat insulation layer <NUM> made of a brittle material. In addition, although the base layer <NUM> similarly bends, the bending of the base layer <NUM> does not cause a problem because the base layer <NUM> according to the present embodiment is made of ductile material which is hard to be damaged even if bend occurs.

In order to reduce the above-described bending of the heat insulation layer <NUM>, as illustrated in <FIG>, it is preferable to set a gap D between the protrusion 23f and the heat insulation layer <NUM> in a direction intersecting the thickness direction and in a side in which the pressure roller presses the heater <NUM>, that is, a right side of the protrusion 23f in <FIG>. Since setting the gap D between the protrusion 23f and the heat insulation layer <NUM> described above results in arrangement of the heat insulation layer <NUM> to a region that does not cause bending, the heat insulation layer <NUM> does not bend and separate from the heater holder <NUM>, and the heater holder <NUM> contacts the heat insulation layer <NUM>. This avoids breaking the heat insulation layer <NUM> due to the bending. On the other hand, in an example illustrated in <FIG>, since the above-described gap D is not sufficiently disposed, the heat insulation layer <NUM> separates from the bottom portion 23a of the recessed portion <NUM> in the side in which the pressure roller presses the heater <NUM>, that is, the right side of the protrusion 23f in <FIG>, and the bending of the heat insulation layer <NUM> increases.

Moreover, contrary to the above-described example illustrated in <FIG>, as illustrated in <FIG>, the heat insulation layer <NUM> may be thicker than the target thickness (that is the same thickness as the height of the protrusion 23f). In this case, when the heater <NUM> is accommodated in the recessed portion <NUM> of the heater holder <NUM>, as illustrated in <FIG>, the back-side surface of the heater <NUM> that is the base layer <NUM> separates from the protrusion 23f of the heater holder <NUM>. However, as illustrated in <FIG>, when the gap D is disposed between the protrusion 23f and the heat insulation layer <NUM> in the direction intersecting with the thickness direction, and when the connector <NUM> is connected to the heater <NUM>, a pressing force G of the contact terminal <NUM> that presses against the electrode <NUM> bends the heater <NUM> downward in <FIG> and causes the back side surface of the heater <NUM> to contact the protrusion 23f. As described above, even when the heat insulation layer <NUM> becomes thicker than the target thickness, setting the gap D described above enables the heater <NUM> to be bent by the pressing force G of the contact terminal <NUM> and causes the back-side surface of the heater <NUM> to contact the protrusion 23f. This enables the protrusion 23f to support the back-side surface of the heater <NUM> and lead the contact pressure of the contact terminal <NUM> with respect to the electrode <NUM> to be stable.

In addition, setting the gap D disposed between the protrusion 23f and the heat insulation layer <NUM> in a direction intersecting the thickness direction as in the example illustrated in <FIG> avoids interference between the protrusion 23f and the heat insulation layer <NUM> (the edge of the hole 40a), which is caused by dimensional tolerances of the heat insulation layer <NUM> and the protrusion 23f (dimensional tolerances in the direction intersecting the thickness direction). Additionally, in the configuration in which the protrusion 23f is inserted into the hole 40a of the heat insulation layer <NUM> as in the present embodiment, it is desirable to provide the gap D between the protrusion 23f and the heat insulation layer <NUM> along all-round the hole 40a.

The number of protrusions 23f is not limited to one and may be more than one. For example, as in the example illustrated in <FIG>, two protrusions 23f may be provided and arranged on portions corresponding to the respective electrode <NUM>. The two protrusions 23f separately disposed on the portions corresponding to two electrodes <NUM>, respectively, can reliably support the portions corresponding to electrodes <NUM>, respectively. Preferably, each protrusion 23f is disposed corresponding to at least the contact point C in each electrode <NUM>. The above-described configuration can reduce a production cost because the above-described configuration can set tip areas of the protrusions 23f that need high dimension accuracy smaller than the configuration in which one protrusion 23f supports the portion corresponding to each electrode <NUM> as illustrated in <FIG>.

As in another example illustrated in <FIG>, three protrusions 23f arranged to form triangle apexes may be provided to support the back-side surface of the base layer <NUM>. This case can further reduce the production cost because the tip area of each protrusion 23f can be further reduced (for example, because each protrusion 23f can be made spherical, to provide point contact with the base layer <NUM>).

As in the heater <NUM> illustrated in <FIG>, the holes 40a in the heat insulation layer <NUM> may be separately formed in portions corresponding to the respective electrodes <NUM>. As described above, individually forming the holes 40a in the portions corresponding to the respective electrode <NUM> enables the portion in which the heat insulation layer <NUM> is omitted to be minimized, which suppresses the decrease in rigidity that is caused by omitting the heat insulation layer <NUM>. In this case, as illustrated in <FIG>, the heater holder <NUM> illustrated in <FIG> is preferably applied as the heater holder <NUM>. As illustrated in <FIG>, a plurality of protrusions 23f disposed on the heater holder <NUM> is inserted into a plurality of holes 40a formed in the heat insulation layer <NUM>, and each of the protrusions 23f supports the back-side surface of the base layer <NUM>.

As in an example illustrated in <FIG>, the heat insulation layer <NUM> may be disposed on a portion corresponding to the heat generator <NUM> and a vicinity of the heat generator <NUM>. This case enables to reduce a size of the heat insulation layer <NUM> and the production cost.

Another embodiment of the present disclosure is now described.

In the above-described embodiment (a first embodiment), the heat insulation layer <NUM> that is one of the layers in the heater <NUM> is omitted (not provided) in the portion corresponding to the electrodes <NUM>, but in a second embodiment of the present disclosure, a part of the layers in the heater <NUM> is partially made thin.

Specifically, as illustrated in <FIG>, in the thickness of the base layer <NUM> that is one of the layers in the heater <NUM>, the portion corresponding to the electrode <NUM> is thinner than the portion corresponding to the heat generator <NUM>. In other words, the base layer <NUM> is disposed in the opposite side with respect to the surface on which the electrode is disposed and forms a single portion having a part corresponding to the electrode <NUM> and a part corresponding to the heat generator <NUM>, and the part corresponding to the electrode <NUM> is thinner than the part corresponding to the heat generator <NUM>. Reducing the thickness of the base layer <NUM> in the portion corresponding to the electrode <NUM> as described above decreases the variation in the thickness of the base layer <NUM> at the portion. Accordingly, the combined tolerances in the thicknesses of layers of the heater decreases in the portion corresponding to the electrode <NUM>, and the variation in the thickness of the heater <NUM> also decreases. Since this enables to reduce the variation in the contact pressure from the contact terminals <NUM> to the electrode <NUM> and easily manage the contact pressure and prevent the contact pressure from being insufficient or excessive, the contact pressure can be set to the appropriate value (that is, within the appropriate range). In the present embodiment, similar to the first embodiment, the protrusion 23f of the heater holder <NUM> is the contact portion that contacts the base layer <NUM>, but there is the slight gap between the bottom portion 23a of the heater holder <NUM> and the base layer <NUM>, and the bottom portion 23a is the portion not in contact with the back surface of the heater <NUM>. Therefore, in the base layer <NUM> according to the present embodiment, the portion in which the contact portion of the heater holder <NUM>, that is, the protrusion 23f contacts the back surface of the heater <NUM> is thinner than the portion in which the contact portion that is the protrusion 23f does not contact the back surface of the heater <NUM>.

Additionally, as illustrated in <FIG>, in the present embodiment, the protrusion 23f that supports the thinly formed portion of the base layer <NUM> from the back side is disposed in the recessed portion <NUM> of the heater holder <NUM>.

The current-carrying connector used in the present embodiment has the same configuration as that of the above-described embodiment (the first embodiment) (see <FIG>). That is, the connector includes the contact terminal <NUM> that sandwiches the heater <NUM> and the heater holder <NUM> together from the front side and the back side and holds the heater <NUM> and the heater holder <NUM>. When the contact terminal <NUM> holds the heater <NUM> and the heater holder <NUM>, the pair of contact portions 72a of the contact terminal <NUM> is pressed against the electrodes <NUM> of the heater <NUM>. In the above-described configuration in which the contact terminal <NUM> sandwiches and holds not only the heater <NUM> but also the heater holder <NUM>, the contact pressure of the contact terminal <NUM> to the electrode <NUM> is affected by not only the variation in the thickness of the heater <NUM> but also the variation in the thickness of the heater holder <NUM>. In this regard, in the present embodiment, as described above, the thickness of the base layer <NUM> decreases at the portion corresponding to the electrode <NUM>, while the thickness of the heater holder <NUM> which is provided with the protrusion 23f increases. However, in the present embodiment, since the heater holder <NUM> is a resin molded article molded by a mold, an error in thickness hardly occurs. Therefore, the variation in the thickness of the heater holder <NUM> caused by the increase in thickness due to the provision of the protrusion 23f hardly affects the contact pressure of the contact terminal <NUM> and does not cause a problem.

A range of the thinly formed base layer <NUM> is preferably in a range including at least a position corresponding to the contact point C (see <FIG>) between the contact terminal <NUM> and the electrode <NUM>. Therefore, the base layer <NUM> may be recessed and thinned only at the portion corresponding to the contact point C and the vicinity thereof. Additionally, similar to the range of the thinly formed base layer <NUM>, the protrusion 23f of the heater holder <NUM> to support the range is preferably disposed at a position corresponding to at least the contact point C between the contact terminal <NUM> and the electrode <NUM>. The number of the protrusions 23f of the heater holder <NUM> to support the thinly formed portion of the base layer <NUM> and a number of the thinly formed portion of the heater holder <NUM> may be more than one, corresponding to the number of the electrodes <NUM>. As in the example illustrated in <FIG>, the protrusion 23f may be arranged to form a vertex of a triangle.

As illustrated in <FIG>, in the present embodiment, there is a gap E between the protrusion 23f and the base layer <NUM> in the direction intersecting the thickness direction. Setting the gap E described above enables to avoid interference between the protrusion 23f and the base layer <NUM>, which is caused by dimensional tolerances of the base layer <NUM> and the protrusion 23f (dimensional tolerances in the direction intersecting the thickness direction).

In the example illustrated in <FIG>, the back-side portion of the base layer <NUM> (the lower portion in <FIG>, or the portion opposite the portion on which the electrode <NUM> is disposed) is changed in the thickness direction to make the base layer <NUM> partially formed. Conversely, as in the example illustrated in <FIG>, the front side portion of the base layer <NUM> (the upper portion in <FIG>) may be changed in the thickness direction to make the base layer <NUM> partially thinner. However, in the example illustrated in <FIG>, a step is formed in the conductor layer <NUM> on the front side, and the shape is complicated. Therefore, it is difficult to form the conductor layer <NUM> by the method of forming the conductor layer <NUM> by screen printing. Therefore, from the viewpoint of ease of formation of the conductor layer <NUM>, as illustrated in <FIG>, it is preferable to change the back-side portion of the base layer <NUM> in the thickness direction.

<FIG> are cross-sectional views illustrating variations of the second embodiment. In each of the variations illustrated in <FIG>, the shape of the step in which the thickness of the base layer <NUM> changes is different compared to the example illustrated in <FIG> described above.

Specifically, in the example illustrated in <FIG>, the step of the base layer <NUM> is a stepped portion <NUM> that is formed in a stepwise shape having a plurality of steps in the thickness direction which becomes thinner in a step-by-step manner from the portion corresponding to the heat generator <NUM> to the portion corresponding to the electrode <NUM>. Forming the step of the base layer <NUM> in the stepwise shape including a plurality of steps enables to make the step (a height) for one step smaller than the step of the base layer <NUM> that is one step as illustrated in <FIG> described above. Therefore, adopting such a configuration enables to form the step (the stepped portion <NUM>) by a method of applying a material paste containing metal powder etc. in a step-like manner while applying masking on the material paste. This method enables to make the base layer <NUM> in lower cost than a method that forms the large step in the example illustrated in <FIG> by cutting.

In the example illustrated in <FIG>, the step of the base layer <NUM> is an inclined portion <NUM> in which the back-side portion of the base layer inclines in the thickness direction to be the base layer <NUM> gradually thinner from the portion corresponding to the heat generator <NUM> to the portion corresponding to the electrode <NUM>. In this example, the inclined portion <NUM> is a flat surface, but may be a curved surface. Compared with the step formed in <NUM>-degree angle illustrated in <FIG>, the step formed by inclining the base layer <NUM> can avoid stress concentration such as thermal stress in the step and improve the durability of the base layer <NUM>.

As described above, in the second embodiment of the present disclosure, reducing the thickness of the base layer <NUM> that is one of the layers in the heater <NUM> in the portion corresponding to the electrode <NUM> reduces the variation in the thickness of the heater <NUM>, which results in decrease of variation in contact pressure of the contact terminal. Although the example illustrated in <FIG> omits the heat insulation layer <NUM> and the first insulation layer <NUM> in the first embodiment described above, the examples illustrated in <FIG> may include the heat insulation layer <NUM> and the first insulation layer and are not limited by the number of layers in the heater <NUM> and the type (material) of the layers. Therefore, the layer formed thin in the portion corresponding to the electrode <NUM> may be one of the layers in the heater <NUM> which is arbitrarily selected other than the base layer <NUM>. Or, the thicknesses of a plurality of layers arbitrarily selected from the layers in the heater <NUM> and including the base layer <NUM> may be reduced. In short, partially reducing the thickness of at least one of the layers in the heater <NUM> results in a total thickness T4 in the lamination direction from the front side surface of the conductor layer <NUM> at the region corresponding to the electrode <NUM> to the back side surface of the heater <NUM> that is the back side surface of the base layer <NUM> in the example illustrated in <FIG> thinner than a total thickness T3 in the lamination direction from the front side surface of the conductor layer <NUM> at the region corresponding to the heat generator <NUM> to the back side surface of the heater <NUM> that is the back side surface of the base layer <NUM> in the example illustrated in <FIG>. In other words, the total thickness in the lamination direction of the portion including the layers in the heater <NUM> and are layered from the conductor layer <NUM> toward the base layer <NUM> is thinner at the region corresponding the electrode <NUM> (T3) than at the region corresponding to the heat generator <NUM> (T4).

<FIG> is a cross-sectional view illustrating the heater <NUM> and the heater holder <NUM> according to a third embodiment of the present disclosure.

As illustrated in <FIG>, the heater <NUM> according to the third embodiment includes a high thermal conduction layer <NUM> between the base layer <NUM> and the heat insulation layer <NUM>. The high thermal conduction layer <NUM> is made of a material having a thermal conductivity higher than that of the base layer <NUM> and the heat insulation layer <NUM> and has a length substantially equal to the entire heater <NUM> in the longitudinal direction of the heater <NUM>.

Generally, the fixing device has an issue that temperature on the end side of a heat generation area that is the temperature outside an area for passing the sheet is excessively high when the sheet having a width smaller than the heat generation area of the heater <NUM> is continuously passed. To decrease such an excessive rise in temperature on the end side, in the present embodiment, the high thermal conduction layer <NUM> as described above is provided and distributes the heat on the end side that may cause the excessive rise in temperature in the longitudinal direction of the heater <NUM> that is a sheet width direction. As described above, since the high thermal conduction layer <NUM> uniformly distributes the heat of the heater <NUM> in the longitudinal direction, the high thermal conduction layer <NUM> can prevent the heater <NUM> from rising the temperature on the end side even when small-size sheets continuously pass. As a result, print productivity of the small-size sheets can be improved because there are no needs to set the sheet passing wait time or to slow the sheet passing speed in order to avoid the temperature rise on the end side.

In this configuration including the high thermal conduction layer <NUM> according to the present embodiment, as illustrated in <FIG>, the high thermal conduction layer <NUM> is omitted at a portion corresponding to the electrode <NUM> (that is, provided except for the portion corresponding to the electrode <NUM>) to prevent the contact pressure defect (insufficient contact pressure or excessive contact pressure) of the connector <NUM> with respect to the heater <NUM>. Similarly, the heat insulation layer <NUM> is also omitted at the portion corresponding to the electrode <NUM>. In other words, the heat insulation layer <NUM> and the high thermal conduction layer <NUM> are disposed in the opposite side with respect to the surface on which the electrode is disposed, and the heat insulation layer <NUM> and the high thermal conduction layer <NUM> have holes corresponding to the electrode <NUM>. Each hole forms a plurality of portions in each of the heat insulation layer <NUM> and the high thermal conduction layer <NUM>, and the gap formed by the hole exists between the plurality of portions.

As described above, in the present embodiment, partially omitting the heat insulation layer <NUM> and the high thermal conduction layer <NUM> at the portion corresponding to the electrode <NUM> reduces the combined tolerances of the layers in the heater <NUM> and the variation in the contact pressure of the contact terminal <NUM> with respect to the electrode <NUM>. To obtain the above-described advantage, the high thermal conduction layer <NUM> and the heat insulation layer <NUM> are removed at least the portion corresponding to the contact point C between the contact terminal <NUM> and the electrode <NUM> (see <FIG>) in the portion corresponding to the electrode <NUM> and arranged. The current-carrying connector used in the present embodiment has the same configuration as that of the above-described embodiment (the first embodiment) (see <FIG>).

As illustrated in <FIG>, in the present embodiment, the high thermal conduction layer <NUM> and the heat insulation layer <NUM> have holes 50a and 40a in portions corresponding to the electrode <NUM>. Through the holes 50a and 40a, the protrusion 23f disposed on the heater holder <NUM> supports the back-side surface of the base layer <NUM>. The configuration of the heater holder <NUM> according to the present embodiment may be the above-described configuration having two protrusions 23f as illustrated in <FIG> or the above-described configuration having three protrusions 23f as illustrated in <FIG>.

Similar to the heat insulation layer <NUM> illustrated in <FIG> described above, the hole 50a of the high thermal conduction layer <NUM> may be separately disposed on the portion corresponding to the electrodes <NUM>. In this case, minimizing the portion on which the high thermal conduction layer <NUM> is omitted enables providing the high thermal conduction layer <NUM> on a wide area. Or, conversely, the portion on which the high thermal conduction layer <NUM> is provided may be a requisite minimum. Since the high thermal conduction layer <NUM> may be provided at least in the area on which the temperature rise on the end side may occur, for example, similar to the above-described heat insulation layer <NUM> illustrated in <FIG> described above, the high thermal conduction layer <NUM> may be disposed on a region corresponding to the heat generator <NUM> and a vicinity of the heat generator <NUM>. In this case, minimizing the portion on which the high thermal conduction layer <NUM> is provided reduces cost. In addition, since minimizing the portion on which the high thermal conduction layer <NUM> is provided can prevent the heat from transmitting to the electrode <NUM> via the high thermal conduction layer <NUM>, an inexpensive material with low heat resistance may be used as the material of the electrode <NUM>.

<FIG> is a cross-sectional view illustrating a heating body <NUM> and the connector <NUM> according to a fourth embodiment of the present disclosure;.

As illustrated in <FIG>, in the fourth embodiment, the connector <NUM> directly contacts with the back side of the heating body <NUM>. In the above embodiment, the heater holder <NUM> is a contact member that directly contacts the back side of the heating body <NUM>. However, in the present embodiment, the connector <NUM> is the contact member that directly contacts the back side of the heating body <NUM>. In the example illustrated in <FIG>, the housing <NUM> of the connector <NUM> is extended in the longitudinal direction of the heating body <NUM> that is a right direction in <FIG> and bent in the thickness direction of the heating body <NUM> that is an upper direction in <FIG>, and a tip 71a of a bent portion in which the housing <NUM> of the connector <NUM> is bent contacts the back side of the base layer <NUM>. That is, in this case, the tip 71a of the bent portion of the housing <NUM> is the contact portion that contacts the back side of the heating body <NUM>. The heat insulation layer <NUM> is removed a portion corresponding to a portion on which the tip 71a contacts the back side of the heating body <NUM>, and the hole 40a is provided. In other words, the heat insulation layer <NUM> is disposed in the opposite side with respect to the surface on which the electrode is disposed and has a hole corresponding to the contact portion. The hole forms a plurality of portions in the heat insulation layer <NUM>, and the gap formed by the holes exists between the plurality of portions. This can reduce the variation in the contact pressure of the contact terminal <NUM> because the contact pressure of the contact terminal <NUM> against the electrode <NUM> becomes less susceptible to the variation in the contact pressure of the contact terminal <NUM> compared with a configuration in which the heat insulation layer <NUM> does not have the hole 40a on the portion on which the tip 71a contacts the back side of the heating body <NUM>. A configuration of the present embodiment is different from the configuration of the above-described embodiment and has the hole 40a that is the portion removed the heat insulation layer <NUM>, the hole 40a shifted from the position corresponding to the electrode <NUM> in the longitudinal direction of the heater <NUM> or the heating body <NUM>. However, this configuration can also reduce the variation in the contact pressure of the contact terminal <NUM>. The configuration including the portion removed the heat insulation layer <NUM> and shifted from the position corresponding to the electrode <NUM> is considered that the degree of freedom in design is enhanced because this configuration can reduce the variation in the contact pressure even when providing a part that contacts the heating body on the portion corresponding to the electrode <NUM> is difficult, for example, when another component is disposed on the portion corresponding to the electrode <NUM>. The configuration illustrated in <FIG> may be applied to the configuration illustrated in <FIG>, that is, the thickness of layer on the portion on which the tip 71a that is the contact portion of the connector <NUM> contacts the back side of the heating body <NUM> may be thinner than the thickness of layer on the other portion.

The above-described embodiments are illustrative and do not limit this disclosure. It is therefore to be understood that within the scope of the appended claims, numerous additional modifications and variations are possible to this disclosure otherwise than as specifically described herein. Therefore, the above-described embodiments and their variations may be combined as appropriate. The above-described embodiment is configured by either removing a part of at least one of the layers in the heater or reducing a thickness of the part of at least one of the layers in the heater, but the heater may be configured by removing a part of at least one of the layers in the heater and reducing a thickness of the part of another one of the layers in the heater. The plurality of layers in the heater <NUM> may be the base layer and layers having different thermal conductivity from the base layer. The first insulation layer may be provided on the opposite side of the layer having different thermal conductivity from the base layer, or the second insulation layer may be provided on the surface on which the electrode and the heat generator connected to the electrode are disposed. The layer having different thermal conductivity from the base layer may have higher thermal conductivity than the base layer or lower thermal conductivity than the base layer.

In the above-described embodiment, although the rectangular hole 40a is formed in a part of the heat insulation layer <NUM> by removing the part of the heat insulation layer <NUM>, the layer removed the part of itself as described above is not limited to the low thermal conduction layer having lower thermal conductivity than the base layer <NUM>, such as the heat insulation layer <NUM> described above. As such the layer, for example, contrary to the heat insulation layer <NUM>, a heat-equalization layer (thermally conductive metal layer) may be used that is made of a material having a thermal conductivity higher than that of the base layer <NUM>, such as copper, aluminum, silver, bronze. That is, the layer removed a part of itself may be the layer having higher thermal conductivity than the base layer <NUM> (that is, the heat-equalization layer or the thermally conductive metal layer), or the layer having lower thermal conductivity than the base layer <NUM> (that is, the heat insulation layer or the low thermal conduction layer). That is, the layer removed a part of itself may be the layer having different thermal conductivity from the base layer <NUM>.

As in the example illustrated in <FIG>, the first insulation layer <NUM> and the second insulation layer <NUM> may be removed, and the heater <NUM> may be configured by the heat insulation layer <NUM>, the base layer <NUM>, and the conductor layer <NUM>. As in the example illustrated in <FIG>, the heater <NUM> may have a configuration including a lowest layer <NUM> on the back side of the heat insulation layer <NUM> in addition to the heat insulation layer <NUM>, the base layer <NUM>, the first insulation layer <NUM>, the conductor layer <NUM>, and the second insulation layer <NUM>. In each of the examples illustrated in <FIG>, the heat insulation layer <NUM> is removed the portion corresponding to the electrode <NUM>.

In short, in the heater according to the present disclosure, the plate <NUM> provided with the electrode <NUM> and the heat generator <NUM> may be configured by the heat insulation layer <NUM>, the base layer <NUM>, and the first insulation layer <NUM> as illustrated in <FIG>, or by the heat insulation layer <NUM> and the base layer <NUM> as illustrated in <FIG>. Or, the plate <NUM> may be configured by the lowest layer <NUM>, the heat insulation layer <NUM>, the base layer <NUM>, and the first insulation layer <NUM> as illustrated in <FIG>. In addition, the layer removed the part of itself or thinly formed the part of itself, which is at least one layer of the plurality of layers included in the plate <NUM> described above, may be an outermost layer to the surface on which the electrode <NUM> is disposed (see <FIG> and <FIG>), or a layer between the surface on which the electrode <NUM> is disposed and the outermost layer (see <FIG>). That is, a position of the layer removed the part of itself or thinly formed the part of itself does not matter. For example, in the example illustrated in <FIG>, the layer removed the part of itself may be the lowest layer <NUM> or the base layer <NUM> in addition to the heat insulation layer <NUM>.

In the above-described embodiment, the heater <NUM> has the two heat generators <NUM> are disposed parallel to each other in the longitudinal direction of the base layer <NUM> and electrically connected in series, but, as in the example illustrated in <FIG>, the heater <NUM> may have a plurality of heat generators <NUM> arranged at intervals in the longitudinal direction of the base layer <NUM> (that is also a belt width direction). As in this example, each heat generator <NUM> may be formed in a shape having a plurality of folded portions and electrically connected in parallel to a pair of electrodes <NUM> disposed at both ends in the longitudinal direction of the base layer <NUM>. In the heater <NUM> having the plurality of heat generators <NUM>, the gap between the heat generators <NUM> adjacent to each other is preferably <NUM> or more, more preferably <NUM> or more from the viewpoint of maintaining the insulation between the heat generators <NUM>. In addition, the gap between the heat generators <NUM> adjacent to each other is preferably <NUM> or less, more preferably <NUM> or less from the viewpoint of reducing temperature unevenness along the longitudinal direction because too large gap between the heat generators <NUM> adjacent to each other easily causes a temperature drop in the gap.

Moreover, in the above-described embodiment, although electrode <NUM> of heater <NUM> is connected to the heat generator <NUM>, the present disclosure is not limited to this. For example, the present disclosure is also applicable to a configuration in which the electrode is connected to a temperature sensor such as a thermistor.

The present disclosure is also applicable, for example, to fixing devices as illustrated in <FIG>, in addition to the fixing device illustrated in <FIG>. The configuration of each fixing devices illustrated in <FIG> is briefly described below.

First, the fixing device <NUM> illustrated in <FIG> includes a pressurization roller <NUM> opposite the pressure roller <NUM> with respect to the fixing belt <NUM> and heats the fixing belt <NUM> sandwiched by the pressurization roller <NUM> and the heater <NUM>. On the other hand, in the side of the pressure roller <NUM>, a nip formation pad <NUM> is disposed inside the inner circumferential surface of the fixing belt <NUM>. The stay <NUM> supports the nip formation pad <NUM>, and the nip formation pad <NUM> and the pressure roller <NUM> sandwiches the fixing belt <NUM> to form the nip N.

Next, the fixing device <NUM> illustrated in <FIG> is omitted the above described pressurization roller <NUM> and includes the heater <NUM> configured by an arc-shaped plate having a curvature of the fixing belt <NUM> to keep a circumferential contact length between the fixing belt <NUM> and the heater <NUM>. The fixing device <NUM> illustrated in <FIG> is identical to the fixing device <NUM> illustrated in <FIG> in terms of the others.

Lastly, the fixing device <NUM> illustrated in <FIG> includes a pressing belt <NUM> in addition to the fixing belt <NUM> and has a heating nip (a first nip) N1 and the fixing nip (a second nip) N2 separately. That is, the nip formation pad <NUM> and the stay <NUM> are disposed opposite the fixing belt <NUM> with respect to the pressure roller <NUM>, and the pressing belt <NUM> is rotatably arranged to wrap around the nip formation pad <NUM> and the stay <NUM>. The sheet P passes through the fixing nip N2 between the pressing belt <NUM> and the pressure roller <NUM> and is applied to heat and pressure, and the image is fixed on the sheet P. The fixing device <NUM> illustrated in <FIG> is identical to the fixing device <NUM> illustrated in <FIG> in terms of the others.

As described above, in the fixing device according to the present disclosure, the portion corresponding to at least one part of the electrode (that is, the contact point C) in the layer is removed or made thinner. Or, the portion in the one layer is removed, and the portion in the other layer is made thinner. These can reduce the variation in thickness of the heater and prevent contact pressure failure of the connector with respect to the heater. Without adopting the configuration in which the contact terminal is movable relative to the housing, adopting the configuration of the present disclosure enables to ensure the electrical connection between the connector and the heater, simplify the configuration of the connector, and prevent the heating device from increasing the cost and the size.

In the configuration as illustrated in <FIG>, in which the connector <NUM> elastically contacts only one side of the heater <NUM> in the thickness direction (only the upper surface side of the heater <NUM> in <FIG>), the large variation in the thickness of the heater tends to cause the larger variation in the contact pressure of the connector with respect to the heater than in the configuration in which the connector elastically contacts both sides of the heater in the thickness direction. However, even in the configuration in which the connector <NUM> elastically contacts only one side of the heater <NUM> in the thickness direction, applying the present disclosure can stabilizes the contact pressure of the connector with respect to the heater. That is, without adopting a connector which elastically contacts the heater from both sides in the thickness direction, the present disclosure can simplify the configuration and reduce the cost because the contact pressure defects of the connector with respect to the heater can be effectively prevented.

In addition to the above-described fixing device, the heater and the heating device according to the present disclosure is also applicable to a dryer to dry ink applied to the sheet and a coating device (a laminator) that heats, under pressure, a film as a covering member onto the surface of the sheet such as paper. The image forming apparatus <NUM> according to the embodiments of the present disclosure may be a copier, a facsimile machine, a multifunction peripheral (MFP) having at least two of copying, printing, scanning, facsimile, and plotter functions in addition to the printer. Embodiments of the present disclosure may be applied to an ink jet type image forming apparatus in addition to the electrophotographic type image forming apparatus.

Claim 1:
A heating device (<NUM>) comprising a heater (<NUM>) to contact a contact portion (23f, 71a) of a contact member (<NUM>, <NUM>), comprising:
an electrode (<NUM>);
a heat generator (<NUM>); and
a plurality of layers (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) including
a first layer (<NUM>) on which the electrode (<NUM>) and the heat generator (<NUM>) are disposed, and
at least one layer (<NUM>, <NUM>, <NUM>) disposed in an opposite side with respect to a surface on which the electrode (<NUM>) is disposed,
wherein
(i) the at least one layer (<NUM>, <NUM>) includes, in an opposite side with respect to a surface on which the electrode (<NUM>) is disposed, a plurality of portions separated by a gap (40a) between the plurality of portions at a position at which the contact portion (23f, 71a) of the contact member (<NUM>, <NUM>) contacts the heater (<NUM>),
the heating device (<NUM>) comprises the contact member (<NUM>, <NUM>), wherein either
the contact member is a heater holder (<NUM>) configured to hold the heater (<NUM>) and the contact portion is a protrusion (23f) of the heater holder (<NUM>); or
the contact member is a housing (<NUM>) of a connector (<NUM>), wherein the connector (<NUM>) is configured to supply power to the heat generator (<NUM>) of the heater (<NUM>) via contact between the electrode (<NUM>) and a contact terminal (<NUM>) of the connector (<NUM>), and the contact portion is a contact portion (71a) of the housing (<NUM>); and/or
(ii) the at least one layer includes a base layer (<NUM>) made of a metal material and including a single portion, a thickness of a first part of the single portion being thinner than a thickness of a second part of the single portion, wherein the first part of the single portion is at a position at which the contact portion (23f, 71a) contacts the heater (<NUM>), and the second part of the single portion is at a position at which the contact portion (23f, 71a) does not contact the heater (<NUM>).