JP2021156982A - Heater, fixing device, and image forming apparatus - Google Patents

Abstract

To avoid the influence of irregularities of a resistor.SOLUTION: In a heater that transfers heat to a member to be heated (fixing belt 310) through one face of a heating member 330 having a substrate (substrate layer 331) that has a longitudinal direction, a plurality of resistors (heat blocks 337a, 337b) that are disposed directly or indirectly on the substrate, and an insulating member (second insulating layer 335) that covers the resistors, at least one of the plurality of resistors has a resistor conductor lamination part (resistance adjustment part 338) in which a conductor is provided on the resistor or a resistor high resistor lamination part in which a high resistor is provided on the resistor, and a surface having higher profile irregularity than flatness within a predetermined range including these lamination parts is provided on one face of the heating member.SELECTED DRAWING: Figure 3B

Description

The present invention relates to a heating device, a fixing device, and an image forming device, and more particularly to a heating device, a fixing device, and an image forming device in which a conductor is provided on a resistor to adjust a resistance value (heat generation density).

Various types of fixing devices used in electrophotographic image forming devices are known. One of them is a model in which a thin-walled fixing belt having a low heat capacity is directly heated by a heating member. This heating member is composed of a base material, a resistor (planar heating element) and an insulating member. A pressure roller as a pressurizing member is arranged on the outside of the fixing belt, and the fixing nip is formed by crimping the pressurizing roller to the heating member with the fixing belt sandwiched between them.

The planar heating element is formed on the substrate by screen printing using a conductive paste. Resistors of planar heating elements range from simple ones that make one round trip or one pass in the longitudinal direction of the base material, to multiple heat blocks having meandering resistors arranged in the longitudinal direction of the base material and connected in parallel. There is something that I did. In the latter case, by energizing and heating only a desired heat block corresponding to a plurality of paper sizes, it is possible to increase productivity (number of sheets to be passed per hour) while suppressing an increase in temperature at the end of the fixing belt. The "meandering shape" refers to a winding shape having at least one folded portion. Further, the "heat block" refers to a meandering (or sheet-shaped) resistor whose both ends are connected to a feeder line.

In order to make the heat generation density of the heat blocks uniform, it has been proposed to provide a conductor in the resistor to adjust the difference in resistance value or heat generation density between the heat blocks (Patent Documents 1 and 2). However, if a conductor is provided on the resistor, unevenness is formed on the surface of the insulating member in contact with the fixing belt, so that the unevenness tends to cause notable fixing defects and image defects such as gloss streaks. In addition, uneven heating due to unevenness is likely to occur.

The present invention has been made in view of such a situation, and an object of the present invention is to avoid the influence of unevenness of the resistor.

In order to solve the above problems, the heating device of the present invention comprises a base material having a longitudinal direction, a plurality of resistors directly or indirectly arranged on the base material, and an insulating member covering the resistors. In a heating device that transfers heat to a member to be heated through one surface of the heating member, at least one of the plurality of resistors has a resistor conductor laminated portion in which a conductor is provided on the resistor, and the resistor conductor is provided. It is characterized in that a surface having a surface accuracy higher than the flatness of a predetermined range including the laminated portion is provided on one surface of the heating member.

According to the present invention, it is possible to avoid the influence of the unevenness of the resistor.

It is a schematic block diagram of the image forming apparatus which concerns on embodiment of this invention. It is a principle figure of the image forming apparatus which concerns on embodiment of this invention. It is a schematic block diagram of the fixing device. It is a top view of the heating member. It is sectional drawing which made the fixing belt sliding contact with the back side of a heating member. It is sectional drawing which made the fixing belt sliding contact with the heat generating side of a heating member. It is a perspective view of the end portion of a heating member. It is a top view of the heating member which has a meandering resistor. It is a plan view of the heating member which has a sheet-like resistor, and is the plan view before (a) and after (b) forming a resistance adjusting part. It is a top view of the heating member which has a meandering resistor. (A) and (b) are plan views before and after forming the anti-adjustment portion of the heating member having a sheet-shaped resistor, and (c) is a cross-sectional view of (b). It is a plan view of the heating member which has a meandering resistor, and is the plan view before (a) and after (b) forming a resistance adjusting part. It is a plan view of the heating member which has a meandering resistor, and is the plan view before (a) and after (b) forming a resistance adjusting part. It is a top view of the heating member which has a sheet-like resistor. It is a perspective view of the fixing device. It is a side view of the fixing device. It is an exploded perspective view of the fixing device. It is a perspective view of a heating device. It is an exploded perspective view of a heating device. It is a top view of the heating member. It is an exploded perspective view of a heating member. It is a rear view of the heating member which has a high thermal conductive layer. It is a figure which shows the state which attached the connector to a heating member and a heater holder. It is a figure which shows the example which the heating part was connected in parallel. It is a figure which compares and shows the temperature distribution when the heating member is displaced and the temperature distribution when the heating member is not displaced. It is a figure which shows the example which has the electrode part at both ends of the heating member. It is a figure which shows the example which the width of the electrode part is different between one end side and the other end side of a heating member. It is a figure which shows the positioning hole and the positioning projection enlarged. It is a figure which shows the example which formed the opening side of a positioning hole wide. It is a figure which shows the example which provided the positioning protrusion in the heating member. It is a figure which shows the example which made up the positioning hole by a through hole. It is a figure which shows the mode that the heating member is positioned in the lateral direction by the rotation of a fixing belt. It is a figure which shows the example which a positioning hole is provided in the side surface part on the upstream side in the belt rotation direction. It is a figure which shows the example which a positioning hole is provided in the side surface part on the downstream side in the belt rotation direction. It is a schematic diagram which disassembled the fixing device. It is a figure which shows the structure which the positioning reference of a paper and each positioning part are set to the same side. It is a figure which shows the example which formed the small cross-sectional part by partially thinning the base material layer. It is a figure which shows the structure of another fixing device. It is a figure which shows the structure which positioned the heating member directly in the side wall part. It is a figure which shows the structure in which a heating member is directly positioned by a stay. It is a figure which shows the example which provided the high heat conduction member on the side opposite to the end side where the positioning part of a heating member was provided. It is a figure which shows the structure of another fixing device. It is a figure which shows the structure of the other fixing device. It is a figure which shows the structure of still another fixing device. It is the schematic of the electrophotographic printer which has a heat roller.

Hereinafter, the heat member, the fixing device, and the image forming device (laser printer) according to the embodiment of the present invention will be described with reference to the drawings. The laser printer is an example of an image forming apparatus, and it goes without saying that the image forming apparatus is not limited to the laser printer. That is, the image forming apparatus can be configured as any one of a copying machine, a facsimile, a printer, a printing machine, and an inkjet recording apparatus, or a compound machine in which at least two or more of these are combined.

The same or corresponding parts in each drawing are designated by the same reference numerals, and the duplicated description thereof will be appropriately simplified or omitted. Further, the dimensions, materials, shapes, relative arrangements thereof, etc. in the description of each component are examples, and the scope of the present invention is not intended to be limited thereto unless otherwise specified.

In the following embodiments, the "recording medium" is described as "paper", but the "recording medium" is not limited to paper (paper). The "recording medium" includes not only paper but also transparencies, cloths, metal sheets, plastic films, and prepreg sheets in which carbon fibers are preliminarily impregnated with resin.

A medium to which a developing agent or ink can be attached, a recording paper, and a recording sheet are all included in the "recording medium". In addition to plain paper, "paper" also includes thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, and the like.

Further, "image formation" used in the following description means not only giving an image having a meaning such as characters or figures to a medium, but also giving an image having no meaning such as a pattern to the medium. Also means.

(Laser printer configuration)
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus may be a printer, a copying machine, a facsimile, or a multifunction device thereof.

The image forming apparatus 100 shown in FIG. 1 includes four image forming units 1Y, 1M, 1C, and 1Bk, which are image forming units. Each image forming unit 1Y, 1M, 1C, 1Bk is configured to be detachable from the image forming apparatus main body 103, and develops different colors of yellow, magenta, cyan, and black corresponding to the color separation component of the color image. It has the same structure except that it is housed.

Specifically, each image forming unit 1Y, 1M, 1C, 1Bk is formed on a drum-shaped photoconductor 2 as an image carrier, a charging device 3 for charging the surface of the photoconductor 2, and a surface of the photoconductor 2. It includes a developing device 4 that supplies toner as a developing agent to form a toner image, and a cleaning device 5 that cleans the surface of the photoconductor 2.

Further, the image forming apparatus 100 is formed on each photoconductor 2, an exposure apparatus 6 that exposes the surface of each photoconductor 2 to form an electrostatic latent image, a paper feeding device 7 that supplies paper P as a recording medium, and each photoconductor 2. A transfer device 8 for transferring the transferred toner image to the paper P, a fixing device 300 for fixing the toner image transferred to the paper P, and a paper ejection device 10 for discharging the paper P to the outside of the device are provided.

The transfer device 8 includes an endless intermediate transfer belt 11 as an intermediate transfer body stretched by a plurality of rollers, and four primary transfer members for transferring a toner image on each photoconductor 2 to the intermediate transfer belt 11. It has a primary transfer roller 12 and a secondary transfer roller 13 as a secondary transfer member that transfers the toner image transferred on the intermediate transfer belt 11 to the paper P. Each of the plurality of primary transfer rollers 12 is in contact with the photoconductor 2 via the intermediate transfer belt 11.

As a result, the intermediate transfer belt 11 and each photoconductor 2 come into contact with each other, and a primary transfer nip is formed between them. On the other hand, the secondary transfer roller 13 is in contact with one of the rollers for tensioning the intermediate transfer belt 11 via the intermediate transfer belt 11. As a result, a secondary transfer nip is formed between the secondary transfer roller 13 and the intermediate transfer belt 11.

Further, in the image forming apparatus 100, a paper conveying path 14 for conveying the paper P sent out from the paper feeding device 7 is formed. A pair of timing rollers 15 are provided on the way from the paper feeding device 7 to the secondary transfer nip (secondary transfer roller 13) in the paper transport path 14.

Next, the printing operation of the image forming apparatus will be described with reference to FIG.

When instructed to start the printing operation, in each of the image forming units 1Y, 1M, 1C, and 1Bk, the photoconductor 2 is rotationally driven clockwise in FIG. 1, and the charging device 3 causes the surface of the photoconductor 2 to have a uniform height. It is charged to the electric potential. Next, the exposure device 6 exposes the surface of each photoconductor 2 based on the image information of the document read by the document reader or the print information instructed to print from the terminal, so that the potential of the exposed portion is increased. It is lowered to form an electrostatic latent image. Then, toner is supplied from the developing device 4 to the electrostatic latent image, and a toner image is formed on each photoconductor 2.

When the toner image formed on each photoconductor 2 reaches the primary transfer nip (position of the primary transfer roller 12) as each photoconductor 2 rotates, the intermediate transfer belt is rotationally driven counterclockwise in FIG. It is transferred to 11 so as to sequentially overlap. Then, the toner image transferred onto the intermediate transfer belt 11 is conveyed to the secondary transfer nip (position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates, and is conveyed at the secondary transfer nip. Transferred to paper P.

This paper P is supplied from the paper feeding device 7. The paper P supplied from the paper feeding device 7 is temporarily stopped by the timing roller 15 and then conveyed to the secondary transfer nip at the timing when the toner image on the intermediate transfer belt 11 reaches the secondary transfer nip. Thus, a full-color toner image is supported on the paper P. Further, after the toner image is transferred, the toner remaining on each photoconductor 2 is removed by each cleaning device 5.

The paper P on which the toner image is transferred is conveyed to the fixing device 300, and the toner image is fixed on the paper P by the fixing device 300. After that, the paper P is ejected to the outside of the paper ejection device 10 to complete a series of printing operations.

(Principle of laser printer)
FIG. 2A is a principle diagram of a laser printer as an embodiment of an image forming apparatus 100 provided with the fixing apparatus 300 of the present invention. The image forming apparatus 100 includes an image carrier 2 (for example, a photoconductor drum) and a drum cleaning apparatus 5. Further, a charging device 3 as a charging means for uniformly charging the surface of the image carrier, a developing device 4 as a developing means for performing visible image processing of an electrostatic latent image formed on the image carrier, and an image carrier. It has a transfer means TM disposed below the body 2, a static eliminator, and the like.

The exposure apparatus 6 is arranged above the image carrier 2. The exposure apparatus 6 performs write scanning according to the image information, that is, reflects the laser beam Lb from the laser diode by the mirror 7a based on the image data and irradiates the image carrier 2.

The paper feeding device 50 having a tray for loading the paper P is installed below the image forming device 100. The paper feeding device 50 can accommodate a large number of sheets P as a recording medium in a bundle, and is unitized together with a paper feeding roller 60 as a means for transporting the paper P.

A resist roller pair 250 as a separation and transporting means is arranged on the downstream side of the paper feed roller 60. The paper P fed from the paper feeding device 50 is temporarily stopped by the resist roller pair 250. By this temporary stop, a slack is formed on the tip side of the paper P, and the skew of the paper P is corrected.

The paper P, which is abutted against the resist roller pair 250 and has a slack at the tip, is sent to the transfer nip N of the transfer means TM at the timing when the toner image on the image carrier 2 is suitably transferred. Then, in the paper P that has been sent out, the toner image on the image carrier 2 is electrostatically transferred to a desired transfer position by the bias applied at the transfer nip N.

A fixing device 300 is arranged on the downstream side of the transfer nip N. The fixing device 300 includes a fixing belt 310 as a fixing member including a halogen heater as a heating element described later, and a pressure roller 320 as a pressure member that rotates while abutting on the fixing belt 310 at a predetermined pressure. I have.

(Laser printer operation)
Next, the basic operation of the laser printer according to the present embodiment will be described. The paper feed roller 60 rotates in response to the paper feed signal from the control unit of the image forming apparatus 100. The rotation of the paper feed roller 60 separates the topmost paper of the bundled paper P loaded on the paper feed device 50 and feeds it to the paper feed path.

When the tip of the fed paper P reaches the nip of the resist roller pair 250, it forms a slack and stands by in that state. Then, the optimum timing (synchronization) for transferring the toner image on the image carrier 2 to the paper P is set, and the tip skew of the paper P is corrected.

The charging device 3 uniformly charges the surface of the image carrier 2 to a high potential. Then, the exposure apparatus 6 reflects the laser beam Lb based on the image data by the mirror 6a and irradiates the surface of the image carrier 2.

On the surface of the image carrier 2 irradiated with the laser beam Lb, the potential of the irradiated portion is lowered to form an electrostatic latent image. The developing apparatus 4 has a developer carrier 4a that supports a developer containing toner, and an electrostatic latent image is formed on the unused black toner supplied from the toner bottle via the developer carrier 4a. The image carrier 2 is transferred to the surface portion of the image carrier 2.

The image carrier 2 to which the toner has been transferred forms (develops) a toner image on its surface. Then, the toner image formed on the image carrier 2 is transferred to the paper P by the transfer means TM.

The drum cleaning device 5 removes residual toner adhering to the surface of the image carrier 2 after the transfer process with the cleaning blade 5a. The removed residual toner is collected in the waste toner accommodating portion.

The paper P on which the toner image is transferred is conveyed to the fixing device 300. The paper P conveyed to the fixing device 300 is sandwiched between the fixing belt 310 and the pressure roller 320, and the unfixed toner image is fixed to the paper P by heating and pressurizing. The paper P on which the toner image is fixed is sent out from the fixing device 300.

(Fixing device)
Subsequently, the configuration of the fixing device 300 will be described.

As shown in FIG. 2B, the fixing device 300 according to the present embodiment has a fixing belt 310 made of an endless belt member as a fixing member and an opposing surface that contacts the outer peripheral surface of the fixing belt 310 to form a nip portion N. It has a pressure roller 320 as a member and a heating member 330 for heating the fixing belt 310. The heating member 330 is held by the heater holder 340, and the heater holder 340 is reinforced in the longitudinal direction by the stay 350 as a reinforcing member.

The fixing belt 310 is composed of a flexible sleeve-shaped rotating member, and has, for example, a cylindrical substrate made of polyimide (PI) having an outer diameter of 25 mm and a thickness of 40 to 120 μm. On the outermost surface layer of the fixing belt 310, a mold release layer having a thickness of 5 to 50 μm is formed of a fluororesin such as PFA or PTFE in order to enhance durability and ensure mold release.

An elastic layer made of rubber or the like having a thickness of 50 to 500 μm may be provided between the substrate and the release layer. Further, the substrate of the fixing belt 310 is not limited to polyimide, and may be a heat-resistant resin such as PEEK or a metal substrate such as nickel (Ni) or SUS. The inner peripheral surface of the fixing belt 310 may be coated with polyimide, PTFE or the like as a sliding layer.

The pressure roller 320 has, for example, an outer diameter of 25 mm, a solid iron core metal 321 and an elastic layer 322 formed on the surface of the core metal 321 and a release layer formed on the outside of the elastic layer 322. It is composed of 323 and. The elastic layer 322 is made of silicone rubber and has a thickness of, for example, 3.5 mm. In order to improve the releasability of the surface of the elastic layer 322, it is desirable to form the releasable layer 323 made of a fluororesin layer having a thickness of, for example, about 40 μm.

The heating member 330 is provided in a longitudinal shape along the width direction of the fixing belt 310, and is arranged so as to come into contact with the inner peripheral surface of the fixing belt 310. The heating member 330 may be in non-contact with the fixing belt 310 or indirectly in contact with the fixing belt 310 via a low friction sheet or the like, but it is better to bring the heating member 330 in direct contact with the fixing belt 310. The heat transfer efficiency to the fixing belt 310 is improved.

Further, the heating member 330 can be brought into contact with the outer peripheral surface of the fixing belt 310, but if the outer peripheral surface of the fixing belt 310 is damaged by the contact with the heating member 330, the fixing quality may deteriorate. Therefore, the heating member 330 Should be in contact with the inner peripheral surface of the fixing belt 310.

The heating member 330 includes a base material layer 331, a first insulating layer 332 as an insulating member, a conductor layer 334 having a heat generating portion 333, and a first insulating member, which are sequentially laminated on the nip portion N side of the base material layer 331. It is composed of two insulating layers 335 and a third insulating layer 336 as an insulating member laminated on the opposite side of the base material layer 331.

The base material layer 331 can be made of ceramic. Since ceramic has a coefficient of linear expansion close to that of glass, when glass is used for the insulating layers 332, 335, and 336, the conductor layer 334 is formed due to the deviation between the base material layer 331 and the insulating layers 332, 335, and 336 during thermal expansion. There is a merit that shearing force is hard to be applied. Further, since the thermal conductivity of ceramic is higher than that of metal such as stainless steel, it is advantageous to conduct heat to the fixing belt 310 via the base material layer 331.

The heater holder 340 and the stay 350 are arranged on the inner peripheral side of the fixing belt 310. The stay 350 is made of a metal channel material, and both end portions thereof are supported by both side wall portions of the fixing device 300. Since the surface of the heater holder 340 opposite to the heating member 330 side is supported by the stay 350, the heating member 330 and the heater holder 340 are held and fixed without being significantly bent by the pressing force of the pressurizing roller 320. A nip portion N is formed between the belt 310 and the pressure roller 320.

Since the heater holder 340 tends to be heated to a high temperature by the heat of the heating member 330, it is desirable that the heater holder 340 is made of a heat-resistant material. For example, when the heater holder 340 is made of a heat-resistant resin having low thermal conductivity such as LCP or PEEK, heat transfer from the heating member 330 to the heater holder 340 is suppressed, and the fixing belt 310 can be efficiently heated. ..

The pressure roller 320 and the fixing belt 310 are pressed against each other by a spring as an urging member. As a result, the nip portion N is formed between the fixing belt 310 and the pressure roller 320. Further, the pressurizing roller 320 functions as a driving roller that is rotationally driven by transmitting a driving force from the driving means provided in the image forming apparatus main body 103.

On the other hand, the fixing belt 310 is configured to rotate in a driven manner as the pressure roller 320 rotates. During rotation, the fixing belt 310 slides with respect to the heating member 330. In order to improve the slidability of the fixing belt 310, a lubricant such as oil or grease may be interposed between the heating member 330 and the fixing belt 310.

When the printing operation is started, the pressure roller 320 is rotationally driven, and the fixing belt 310 starts driven rotation. Further, the fixing belt 310 is heated by supplying electric power to the heating member 330. Then, in a state where the temperature of the fixing belt 310 reaches a predetermined target temperature (fixing temperature), as shown in FIG. 2B, the paper P on which the unfixed toner image is carried is the fixing belt 310 and the pressure roller 320. By being conveyed to the space (nip portion N), the unfixed toner image is heated and pressurized and fixed on the paper P.

As shown in FIG. 3A, the heating member 330 has a total of seven heat blocks, five heat blocks 337a on the center side and two heat blocks 337b on both end sides. The "heat block" refers to a meandering (or sheet-like or planar) resistor whose ends are connected to a feeder, and may be arranged directly or indirectly on the base material layer 331. can. The short width of the resistors of each heat block 337a and 337b is composed of resistors having a substantially constant width and thickness and a constant meandering number of times, and is connected in parallel by electrode portions 339a to 339c and feed lines 339d to 339f, which will be described later. Will be done.

Here, "meandering" is a winding shape having at least one folded portion. In the present embodiment, the shape of extending the heating member 330 in the longitudinal direction by a predetermined length, then folding back in the opposite direction and extending by a predetermined length is repeated a plurality of times in the lateral direction of the heating member 330. Further, the "short direction" is a direction orthogonal to the longitudinal direction of the heating member 330, and in the fixing device 300, a direction parallel to the paper passing direction of the paper P.

Two electrode portions 339a and 339c are formed at one end of the heating member 330, and one electrode portion 339b is formed at the other end. The electrode portion 339c is connected to one end of the central heat block 337a by the feeder line 339d, and the electrode portion 339b on the opposite side is connected to the other end of the central heat block 337a by the feeder line 339e. Further, the electrode portion 339a and the electrode portion 339b are connected to both ends of the heat block 337b on both ends by the feeder line 339f and the feeder line 339e.

For the meandering resistor of the heat blocks 337a and 337b, for example, a paste prepared by blending silver palladium (AgPd) or glass powder is applied to the base material layer 331 by screen printing or the like, and then the base material layer 331 is applied. It can be formed by firing. In addition to these, a resistance material of silver alloy (AgPt) or ruthenium oxide (RuO ₂ ) may be used as the material of the resistor.

The feeder line 333b is composed of a conductor having a resistance value smaller than that of the heat generating portion 333. As the material of the feeder line 333b and the electrode portion 333a, silver (Ag) or silver palladium (AgPd) can be used, and the feeder line 333b and the electrode portion 333a are formed by screen printing such a material. There is.

The adjacent ends of the heat blocks 337a and 337b are located at the same inclination and overlap in the lateral direction. As a result, the gap between the heat blocks 337a and 337b in the lateral direction is eliminated, and the temperature unevenness in the fixing belt 310 is eliminated.

The boundary (division position) between the heat block 337a on the center side and the heat block 337b on both ends is set according to the paper size. That is, for example, the central heat block 337a is arranged for transporting A4 paper (width 210 mm) in the vertical direction, and for example, the central heat block corresponds to the case of transporting A3 paper (width 297 mm) in the vertical direction. 337a and heat blocks 337b on both ends are arranged.

Specifically, five central heat blocks 337a are arranged corresponding to the case where A4 paper (width 210 mm) is vertically conveyed with reference to the central portion in the longitudinal direction of the heating member 330. The length l1 of each heat block 337a can be, for example, 43 mm (43 mm × 5 = 215 mm> 210 mm).

Further, the central side heat block 337a and the both end side heat blocks 337b are arranged corresponding to the case where the A3 paper (width 297 mm) is vertically conveyed with reference to the central portion in the longitudinal direction of the heating member 330. The length l2 of the heat blocks 337b on both ends can be, for example, 41.5 mm. (41.5 mm x 2 + 215 mm = 298 mm> 297 mm).

When heat blocks 337a and 337b are connected in parallel, the resistance value (calorific value) per block must be increased by multiplying by the number of blocks. For example, when the total resistance of 10Ω is realized by 7 blocks as shown in FIG. 3A, the resistance value of one heat block is 70Ω. In order to increase the resistance of the heat block in this way, the resistor is meandered to lengthen the energization distance.

As described above, if the lengths of the heat blocks 337a and 337b are different between the center side and both ends for the convenience of setting the division position of the heat block according to the paper size, each heat block 337a is a resistor in the same meandering state. When 337b is configured, the resistance value of the central heat block 337a is larger than the resistance value of the heat blocks 337b on both ends.

Then, when a current is supplied from the common AC power supply to the heat blocks 337a and 337b on the center side and both ends with the same duty, the heat generation density of the center heat block 337a becomes smaller than the heat generation density of the heat blocks 337b on both ends. If the heat generation densities differ between the center side and both end sides in this way, temperature unevenness of the fixing belt 310 occurs and the print quality deteriorates.

Therefore, in the heating member 330 according to the embodiment of the present invention, in order to reduce the resistance value of the central heat block 337a having a relatively large resistance value, the resistance of the central heat block 337a by the resistor conductor laminated portion as shown in FIG. It was decided to provide an adjusting unit 338. The conductor used for the resistance adjusting unit 338 has an electric resistance smaller than that of the resistors constituting the heat blocks 337a and 337b.

By partially providing the resistance adjusting portion 338 in the central heat block 337a, the current path of the heat block 337a is short-circuited at the portion of the resistance adjusting portion 338, and the substantial energization path length of the heat block 337a is reduced to reduce the resistance value. Can be reduced. ^{Then, the width, length or thickness of the resistance adjusting unit 338 is set according to the ratio of the heat generation density [W / mm 2} ] of the heat block 337a on the center side and the heat block 337b on both ends, or the electric resistance and the energization path length. Alternatively, by forming the heat block corresponding to the ratio of the heat generation area (mm ² ), the magnitude of the resistance value of the heat blocks 337a and 337b on the center side and both end sides can be adjusted to make the heat generation density uniform.

Instead of reducing the resistance value of the central heat block 337a, it is also conceivable to make the heat generation density uniform by narrowing the cross section of the resistor of the heat block 337b on both ends and increasing the resistance value. However, in that case, the variation in the resistance value becomes large due to the convenience of screen printing, and there is an influence on the life over time due to the influence of the local increase in heat generation density. Therefore, as described above, it is practical to make the heat generation density uniform by the resistance adjusting unit 338.

As shown in FIG. 3B, the resistance adjusting portion 338 is preferably formed wider than the width in the lateral direction of the heat generating portion (resistor) 333. That is, it is possible to form the resistance adjusting portion 338 more conveniently on both sides of the heat generating portion 333 in the lateral direction by screen printing. On the contrary, when the resistance adjusting portion 338 is formed to be narrower, the resistance adjusting portion 338 is formed to be narrower. This is because the possibility of failure due to a local increase in heat generation density increases, and it is necessary to suppress this.

A plurality of methods are possible for forming the resistance adjusting portion 338. That is,
1) Method of partially overwriting the resistance adjusting portion 338 on the meandering resistor of the heat block 337a 2) After partially forming the resistance adjusting portion 338 on the base material in advance, the meandering shape of the heat block 337a Method of overwriting the resistor 3) A method of partially cutting out the meandering resistor and forming a resistance adjusting portion 338 in the missing part of the resistor.

When the resistance adjusting portion 338 is formed by the methods 1) and 2), only the portion of the resistance adjusting portion 338 rises convexly on the surface side of the heat block 337a by about 3 to 12 μm. Then, for example, when the heating member 330 is used as the fixing device of the image forming apparatus, a convexly raised portion is formed as shown in FIG. 3C, and heat transfer to the fixing belt 310 is hindered.

That is, when the side where the heat blocks 337a and 337b are located is brought into sliding contact with the inner peripheral surface of the fixing belt 310, the contact state with the inner peripheral surface of the fixing belt 310 is changed around the portion raised in a convex shape by the resistance adjusting portion 338. Deteriorate. Therefore, heat transfer to the fixing belt 310 is hindered, and a local rise in the temperature of the heating member may cause fixing failure, gloss streaks, and image unevenness.

Therefore, when the resistance adjusting portion 338 is formed by the methods 1) and 2), the side where the heat blocks 337a and 337b are located is set to the opposite side to the fixing belt 310 as shown in FIG. 3B. Then, one surface (rear surface side) of the heating member 330, which is different from the surface on which the heat blocks 337a and 337b are located, is slidably contacted with the inner peripheral surface of the fixing belt 310.

That is, a heating region for heating the fixing belt 310 as a member to be heated or the paper is formed on the surface of the third insulating layer 336. By using a material having good thermal conductivity (ceramic, etc.) for the base material layer 331 of the heating member 330, it is possible to efficiently heat the fixing belt 310 or the paper even on the back side of the heating member 330. Is.

When the resistance adjustment unit 338 is formed by the method of 3), the resistance adjustment unit is provided in the notched portion of the meandering resistor to ensure reliable conduction between the resistance adjustment unit 338 and the resistors on both sides. It is preferable to overlap the conductor of the connection portion on both sides of the 338 with the resistor. When the conductors are overlapped in this way, the overlapped portion is slightly raised as shown in FIG. 7C, but the third insulating layer 336 on the back surface side of the heating member 330 is slidably contacted with the inner peripheral surface of the fixing belt 310. There is no problem if you let it. This method (3) has an advantage that no extra cost is required because the material of the resistor is reduced by the amount of the notch.

(About flatness)
Next, the flatness of the resistance adjusting unit 338 will be described. "Planeness" is a numerical value indicating the smoothness (uniformity) of a plane, and represents the magnitude of deviation from a geometrically correct plane of a plane feature.

In the present embodiment, in order to prevent fixing defects and gloss streaks, a surface having a surface accuracy higher than the flatness of a predetermined range including the resistance adjusting portion 338 is formed on one surface of the heating member 330, and the surface is used as a member to be heated through the surface. Heat is transferred to the fixing belt 310. Therefore, a method of measuring the flatness in a predetermined range including the resistance adjusting unit 338 will be described below.

As shown in FIG. 3D, it is assumed that the end portion of the resistance adjusting portion 338 in the longitudinal direction of the base material 331 is located at the center of a predetermined range (circular region having a diameter D3). The flatness of the circular region can represent the size of the unevenness in a predetermined range including the resistance adjusting portion 338.

The circular region preferably has a diameter of 3 mm or more and 15 mm or less. It was found that the flatness had poor correlation with abnormal images such as gloss streaks when the measurement range Φ was too large. From the results of the following printing test conducted by the inventor of the present application, it was found that the measurement range of flatness having a high correlation with the abnormal image is Φ3 mm to Φ15 mm.
[Result of printing test]
Diameter of measurement range Less than Φ3mm Φ3mm ~ Φ15mm Φ15mm Super printing test result Defective Good Defective

であった場合には、例えば、

よりも高い面精度を持つ別部材（間接部材）を、抵抗調整部３３８の上に載せる。当該別部材（間接部材）は、例えば図３Ｃの第２絶縁層３３５の上に形成した追加絶縁層で構成することができる。そして当該追加絶縁層を通して定着ベルト３１０に熱伝達する。なお、絶縁層以外の部材であっても、前述のように高い面精度を持つ部材であれば前記別部材（間接部材）を構成可能である。 Therefore, the flatness of a predetermined range including the resistance adjusting unit 338 is preferably measured in a state where the resistance adjusting unit 338 is included in a circular region having a diameter of 3 mm or more and 15 mm or less. To transfer heat to the fixing belt 310 through a surface having a surface accuracy higher than the flatness in a predetermined range including the resistance adjusting unit 338, for example, the following is performed. That is, the flatness of the predetermined range Φ10 mm including both the resistance adjusting portion 338 and the portion without the resistance adjusting portion 338 is determined.

If, for example

Another member (indirect member) having higher surface accuracy is placed on the resistance adjusting unit 338. The separate member (indirect member) can be composed of, for example, an additional insulating layer formed on the second insulating layer 335 of FIG. 3C. Then, heat is transferred to the fixing belt 310 through the additional insulating layer. Even if it is a member other than the insulating layer, the other member (indirect member) can be configured as long as it is a member having high surface accuracy as described above.

As another method, as shown in FIG. 3B described above, the heat blocks 337a and 337b where the resistance adjusting portion 338 is located are placed on the opposite side of the fixing belt 310. Then, one surface (third insulating layer 336 on the back surface side) of the heating member 330, which is different from the surface on which the heat blocks 337a and 337b are located, is slidably contacted with the inner peripheral surface of the fixing belt 310.

Next, an example of a specific forming position of the resistance adjusting portion 338 will be described with reference to the heating member 330 of FIG. The heating member 330 has four heat blocks 337a on the central side and two heat blocks 337b on both end sides. Each heat block 337a and 337b is composed of a resistor having a substantially constant width and thickness and a constant meandering number of times.

The adjacent ends of the heat blocks 337a and 337b are not inclined as shown in FIG. 3A, but by providing a heat equalizing member having good thermal conductivity between the heat blocks 337a and 337b and the base material layer 331. It is possible to eliminate the temperature unevenness in the fixing belt 310.

Two electrode portions 339a and 339c are formed at one end of the heating member 330, and one electrode portion 339b is formed at the other end. The electrode portion 339c is connected to one end of the central heat block 337a as the first resistor by the feeder line 339d, and the opposite electrode portion 339b is connected to the other end of the central heat block 337a by the feeder line 339e. There is. Further, the electrode portion 339a and the electrode portion 339b are connected to both ends of the heat block 337b on both ends as the second resistor by the feeder line 339f and the feeder line 339e.

The boundary (division position) between the heat block 337a on the center side and the heat block 337b on both ends is set according to the paper size as in FIG. 3A. The length of the central heat block 337a is set to 53 mm (53 mm × 4 = 212 mm> 210 mm), for example, in the case of vertically transporting A4 paper (width 210 mm). The length of the heat blocks 337b on both ends is set to 47 mm (47 mm × 2 + 212 mm = 306 mm> 297 mm), for example, in the case of vertically transporting A3 paper (width 297 mm).

In the energization path of the central heat block 337a, resistance adjusting portions 338 are formed one by one with the same length. The resistance adjusting portions 338 are formed so as not to overlap each other in the lateral direction of the heat blocks 337a and to form a gap between the resistance adjusting portions 338 in each heat block 337a.

By forming the resistance adjusting portion 338 in this way, it is possible to eliminate the temperature unevenness in the longitudinal direction of the heat block 337a. In other words, even if the division positions of the heat blocks 337a and 337b are changed, the heat generation density between the blocks can be made uniform depending on the formation state of the resistance adjusting portion 338, so that the degree of freedom in designing the division positions is increased. The resistance adjusting portion 338 of FIG. 4 can be formed by partially overwriting the heat block 337a on the meandering resistor as shown in the drawing, or by the above-mentioned methods 2 to 4. By forming the resistance adjusting portion 338 wider than the resistor of the heat block 337a, reliable conduction can be ensured.

To specifically explain the degree of freedom in designing the division position described above, assuming that the heat generation width in the longitudinal direction of the central heat block 337a in FIG. 4 is l1 (= 53 mm), the resistor is provided by providing the resistance adjusting portion 338. The substantially total energization length of can be set to L1 (= 160 mm).

On the other hand, the heat generation width of the heat blocks 337b on both ends in the longitudinal direction is l2 (= 47 mm) (l1> l2), and the total energization length of the resistor is L2 (= 188 mm). Assuming that the line widths D1 and D2 of the resistors are 1.0 mm and the thickness is the same, the resistance value of the central heat block 337a, which has a relatively large heat generation area, as shown in the L / D ratio comparison formula below. Can be lowered, and the heat generation density can be made uniform.
Comparative formula: L1 / D1 (= 160/1) <L2 / D2 (= 188/1) ... (Equation 1)

FIG. 5 is a plan view of a heating member 330 having heat blocks 337a and 337b composed of a sheet-shaped resistor. FIG. 5A is a plan view before forming the resistance adjusting portion 338 on the central heat block 337a, and FIG. 5B is a plan view after forming the resistance adjusting portion 338.

In the heating member 330, a notch portion of the resistor is formed in the intermediate portion of the heat block 337a in the lateral direction (vertical direction in FIG. 5), and the resistance adjusting portion 338 is formed in the notch portion. Others are the same as in FIG. The resistance adjusting unit 338 can also be formed by the above-mentioned methods 1 and 2.

FIG. 6 is a plan view of a heating member 330 having heat blocks 337a and 337b composed of meandering resistors. The heating member 330 has two electrode portions 339a and 339b, and can supply a common voltage and duty to the heat blocks 337a and 337b on the center side and both end sides.

A resistance adjusting portion 338 is formed in the heat blocks 337a and 337b other than the heat block 337b at the right end of FIG. That is, four resistance adjusting portions 338 are formed in each central side heat block 337a, and one resistance adjusting portion 338 is formed in the left end heat block 337b. The resistance adjusting portion 338 can be formed by the above-mentioned methods 1 to 4.

As the number of resistance adjusting portions 338 increases, the resistance value of the heat block can be significantly reduced. In the illustrated example, assuming the case where the heat generation density of the right end heat block 337b is the highest, the resistance adjusting portion 338 is formed in another heat block so as to match the highest heat generation density.

7 (a) and 7 (b) are plan views of a heating member 330 having heat blocks 337a and 337b composed of sheet-shaped resistors. The heating member 330 is the same as the heating member 330 of FIG. 5 except that the heating member 330 has two electrode portions 339a and 339b and supplies a common voltage and duty to the heat blocks 337a and 337b on the center side and both end sides.

The resistance adjusting portion 338 of FIG. 7B is formed in a notch portion of the resistor formed in the intermediate portion of the heat block 337a in the lateral direction (vertical direction of FIG. 7). As shown in FIG. 7C, the resistance adjusting portions 338 at both ends in the lateral direction may be formed by overwriting the heat generating portion 333 in order to form the resistance adjusting portion 338 with the heat block 337a.

8 (a) and 8 (b) show the states before and after forming the resistance adjusting portion 338 of FIG. The resistance adjusting portion 338 is formed by overwriting the notch portion of the resistor of the heat block 337a of FIG. 8A.

9 (a) and 9 (b) show the states before and after forming the resistance adjusting portion 338 of FIG. As for the method of forming the resistance adjusting portion 338, as shown in the enlarged view of FIG. 6, the resistance adjusting portion 338 is formed by overwriting on the resistor of the heat block 337a and also formed in the notch portion of the resistor of the heat block 337a of FIG. 9A. be able to.

Further, as shown in the enlarged view of FIG. 9B, when the resistance adjusting portion 338 is formed, both ends thereof can be formed so as to overlap the resistor of the heat block 337a only in the lateral direction. In other words, the resistance adjusting portion 338 of FIG. 9B has a set of resistor conductor laminated portions at both ends and a conductor portion sandwiched between the set of resistor conductor laminated portions. By forming in this way, it is possible to prevent the resistance adjusting portion 338 from forming the convex portion as shown in FIG. 3C while ensuring reliable continuity.

FIG. 10 is a plan view of a heating member 330 having heat blocks 337a and 337b composed of a sheet-shaped resistor. The length L2 of one heat block is longer than the length L1 of the other 11 heat blocks.

Since the heat blocks 337a and 337b are connected in parallel, when a common voltage or duty is supplied, the heat generation amount and heat generation density of the heat block of length L2 becomes the heat generation amount and heat generation density of the heat block of other length L1. Is smaller than Therefore, a resistance adjusting portion 338 is formed in the heat block having a length L2.

Although the number of resistance adjusting portions 338 is set to 3 in the illustrated example, it can be formed by a number that makes the heat generation density uniform with other heat blocks having a length L1. The resistance adjusting unit 338 can be appropriately formed by the above-mentioned four methods.

(Measuring method of heat generation density)
The relationship between the heat generation density [W / mm ² ] and the temperature [° C.] of the heat blocks 337a and 337b can be expressed by the following equation (1).
Temperature = (heat generation density / heat transfer coefficient) + air temperature around parts ... (1)
Since the heat transfer coefficient of the heat blocks 337a and 337b and the air temperature around the heating member 330 can be measured almost constantly, ^{the magnitude of the heat generation density [W / mm 2} ] is the temperature of the heating member when energized [W / mm 2]. It can be measured by the magnitude of [℃].

For example, the temperature distribution on the surface of the heating member 330 when the heating member 330 is energized with DC30V is measured with a thermoviewer (for example, FLIR T620 manufactured by FLIR Systems). Then, by comparing the temperatures of the heat blocks 337a and 337b when a certain time elapses after energization (for example, after 10 sec), the magnitude of the heat generation density [W / mm ² ] can be indirectly measured. By appropriately forming the resistance adjusting portion 338 on the heat block whose heat generation density is relatively insufficient by the method described above, the heat generation density of all the heat blocks can be made uniform at low cost.

(Assembly structure of fixing device)
The embodiments of the present invention have been described above. Next, the assembly structure of the fixing device 300 to which the present invention can be applied will be described with reference to FIGS. 11A to 39. As shown in FIGS. 15 to 17 and 25 to 36, the heating member 330 of the fixing device 300 includes a series-connected heat generating portion (resistor) 333 that reciprocates once in the longitudinal direction of the base material layer 331, and FIG. Although it is shown as having a heat generating portion (resistor) 333 of a parallel connection type as described above, the heat generating portion 333 can be replaced with a resistor of the type of the heat block 337 described above.

FIG. 11 is a perspective view of the fixing device, and FIG. 12 is an exploded perspective view thereof. As shown in FIGS. 11 and 12, the device frame 360 of the fixing device 300 includes a first device frame 361 composed of a pair of side wall portions 361a and a front wall portion 361b, and a second device frame 362 composed of a rear wall portion 362a. And have.

The pair of side wall portions 361a are arranged on one end side and the other end side in the width direction of the fixing belt 310 (hereinafter, referred to as "belt width direction"), and the pressure roller 320 is provided by the side wall portions 361a. And both ends of the heating device are supported. A plurality of engaging protrusions 361c are provided on each side wall portion 361a, and each engaging protrusion 361c engages with an engaging hole 362b provided in the rear wall portion 362a, whereby the first device frame 361 and the second device frame 361c are provided. The device frame 362 is assembled.

Further, each side wall portion 361a is provided with an insertion groove 361d for inserting the rotation shaft of the pressure roller 320 and the like. The insertion groove 361d is an abutting portion that opens on the rear wall portion 362a side and does not open on the opposite side.

A bearing 363 that supports the rotating shaft of the pressure roller 320 is provided at the end on the abutting portion side. The pressure roller 320 is rotatably supported by both side wall portions 361a by mounting both ends of the rotating shaft on the bearing 363, respectively.

Further, a drive transmission gear 324 as a drive transmission member is provided on one end side of the rotation shaft of the pressure roller 320. The drive transmission gear 324 is arranged in a state where the pressure roller 320 is supported by the side wall portions 361a and is exposed to the outside of the side wall portion 361a. As a result, when the fixing device 300 is mounted on the image forming apparatus main body 103, the drive transmission gear 324 is connected to the gear provided on the image forming apparatus main body 103 so that the driving force from the drive source can be transmitted. Become.

A pair of support members 364 for supporting the fixing belt 310 and the like are provided at both ends of the heating device in the longitudinal direction. The support member 364 is a device frame of the heating device and is also a part of the device frame 360 of the fixing device 300.

The fixing belt 310 is supported by a support member 364 in a so-called free belt system in a state in which tension in the circumferential direction is basically not applied in a non-rotating state. Further, each support member 364 is provided with a guide groove 364a, and the guide groove 364a is assembled to the side wall portion 361a by entering the guide groove 364a along the edge of the insertion groove 361d of the side wall portion 361a.

Further, a pair of springs 365 as urging members are provided between each support member 364 and the rear wall portion 362a. When the support member 364 is urged toward the pressure roller 320 by each spring 365, the fixing belt 310 is pressed against the pressure roller 320, and the nip portion N is formed between the fixing belt 310 and the pressure roller 320. It is formed.

FIG. 13 is a perspective view of the heating device, and FIG. 14 is an exploded perspective view thereof. As shown in FIGS. 13 and 14, a rectangular accommodating recess 341 for accommodating the heating member 330 is provided on the surface of the heater holder 340 on the fixing belt 310 side (nip portion N side). The heating member 330 is held in a state of being housed in the housing recess 341 by being sandwiched together with the heater holder 340 by a connector described later.

The pair of support members 364 come into contact with the C-shaped belt support portion 364b, which is inserted into the inner circumference of the fixing belt 310 to support the fixing belt 310, and the end surface of the fixing belt 310, and moves in the belt width direction (shifting). ), And a support recess 364d into which both ends of the heater holder 340 and the stay 350 are inserted to support them.

FIG. 15 is a plan view of the heating member 330, and FIG. 16 is an exploded perspective view thereof. In the following description, the fixing belt 310 side (nip portion N side) with respect to the heating member 330 will be referred to as a “front side”, and the heater holder 340 side will be referred to as a “back side”.

As shown in FIGS. 15 and 16, the heating member 330 is provided on the plate-shaped base material layer 331, the first insulating layer 332 provided on the front side of the base material layer 331, and the front side of the first insulating layer 332. A plurality of constituent layers of the conductor layer 334, the second insulating layer 335 that covers the front side of the conductor layer 334, and the third insulating layer 336 provided on the back side of the base material layer 331 are laminated. ing.

The conductor layer 334 includes a pair of heat generating portions 333 composed of a planar resistance heating element, a pair of electrode portions 333a provided on one end side in the longitudinal direction of each heat generating portion 333, and an electrode portion 333a and a heat generating portion 333. It is composed of a plurality of power supply lines 333b connecting the heat generating portions 333 with each other. Further, as shown in FIG. 15, at least a part of each electrode portion 333a is not covered with the second insulating layer 335 and is exposed in order to secure the connection with the connector described later.

Each heat generating portion 333 is formed by, for example, applying a paste containing silver palladium (AgPd), glass powder, or the like to the base material layer 331 by screen printing or the like, and then firing the base material layer 331. Can be done. In addition to these, a resistance material of silver alloy (AgPt) or ruthenium oxide (RuO _{2) may be used as the material of the heat generating portion 333.}

In the present embodiment, the heat generating portions 333 are provided so as to extend in the longitudinal direction of the base material layer 331 in parallel with each other. One end of each heat generating portion 333 (right end portion in FIG. 7) is electrically connected to each other via a feeder line 333b, and the other end portion (left end portion in FIG. 15) of each heat generating portion 333 is different from each other. It is electrically connected to the electrode portion 333a via the feeder line 333b.

The feeder line 333b is composed of a conductor having a resistance value smaller than that of the heat generating portion 333. As the material of the feeder line 333b and the electrode portion 333a, silver (Ag) or silver palladium (AgPd) can be used, and the feeder line 333b and the electrode portion 333a are formed by screen printing such a material. There is.

The base material layer 331 is made of a metal material such as stainless steel (SUS), iron, or aluminum. Further, as the material of the base material layer 331, it is also possible to use ceramic, glass or the like in addition to the metal material. When an insulating material such as ceramic is used for the base material layer 331, the first insulating layer 332 between the base material layer 331 and the conductor layer 334 can be omitted.

On the other hand, the metal material has excellent durability against rapid heating and is easy to process, so that it is suitable for cost reduction. Among the metal materials, aluminum and copper are particularly preferable because they have high thermal conductivity and are less likely to cause temperature unevenness. Further, stainless steel has an advantage that it can be manufactured at a lower cost than these.

Each of the insulating layers 51, 53, 54 is made of heat-resistant glass. Further, as these materials, ceramic, polyimide (PI) or the like can also be used.

Further, as shown in FIG. 17, a high thermal conductivity layer 55 having a higher thermal conductivity than that of the base material layer 331 may be provided on the back surface of the base material layer 331. In this case, the heat of the heating member 330 is dispersed through the high thermal conductive layer 55, so that the temperature unevenness of the heating member 330 can be suppressed. Further, in order to effectively suppress temperature unevenness, it is desirable that the high thermal conductive layer 55 is arranged over the entire region (longitudinal direction and lateral direction) in which the heat generating portion 333 is provided.

In the present embodiment, an alloy such as silver or palladium is used for the heat generating portion 333, the electrode portion 333a, and the feeder line 333b, and has PTC characteristics. The PTC characteristic is a characteristic in which the resistance value increases as the temperature increases (the output of the heating member decreases when a constant voltage is applied).

By using the heat generating portion 333 having PTC characteristics, it is possible to suppress excessive temperature rise due to high output at low temperature and low output at high temperature. For example, if the TCR coefficient of the PTC characteristic is set to about 300 to 4000 ppm / degree, the cost can be reduced while securing the resistance value required for the heating member.

More preferably, the TCR coefficient is set to 500 to 2000 ppm / degree. The TCR coefficient can be calculated by measuring the resistance value at 25 degrees and 125 degrees. For example, if the temperature rises by 100 degrees and the resistance value rises by 10%, the TCR coefficient is 1000 ppm / degree.

Further, as the resistance heating element, a substance having a positive temperature coefficient of resistance, that is, a substance having so-called PTC characteristics may be used. Examples of substances exhibiting such properties include barium titanate (BaTIO ³ ) -based ceramics. In a substance having PTC characteristics, the resistance value decreases as the temperature rises until a certain predetermined temperature is reached, so that the applied power does not decrease and the temperature rises quickly. Further, since the resistance value rises sharply after reaching a predetermined temperature and the applied power is automatically reduced, it has a self-temperature control function without external temperature control using a temperature sensor.

In the present embodiment, the length (width in the longitudinal direction) of the heat generating portion 333 is made longer than the paper width. By doing so, it is possible to prevent the occurrence of fixing defects due to a temperature drop in the vicinity of the edge portion in the paper width direction immediately after the start-up. On the contrary, if the length of the heat generating portion 333 is made too long, an excessive temperature rise may occur in the non-passing region during continuous paper passing, so that the length of the heat generating portion 333 needs to be set appropriately. ..

Specifically, in the present embodiment, the heat generating portion 333 is in a range 0.5 mm to 7 mm larger on one side in the width direction with respect to the letter size 216 mm width of the maximum paper size (maximum recording medium passing width) that can be passed. It is desirable to set the heat generation length to 217 mm to 230 mm). More preferably, the heat generating portion 333 is set in a range of 1 mm to 5 mm larger (heat generation length 219 mm to 226 mm) on one side in the width direction with respect to the maximum paper size. In the present embodiment, the length of the heat generating portion 333 is 221 mm.

FIG. 18 is a perspective view showing a state in which the connector 70 is attached to the heating member 330 and the heater holder 340. As shown in FIG. 18, the connector 70 has a resin housing 71 and a leaf spring contact terminal 72 fixed to the housing 71. The contact terminal 72 has a pair of contact portions 72a that come into contact with each electrode portion 333a of the heating member 330. A power feeding harness 73 is connected to the connector 70 (contact terminal 72).

As shown in FIG. 18, the connector 70 is attached so as to sandwich the heating member 330 and the heater holder 340 together from the front side and the back side. As a result, each contact portion 72a of the contact terminal 72 elastically contacts (presses) the electrode portion 333a of the heating member 330, so that the heat generating portion 333 and the power supply provided in the image forming apparatus are provided via the connector 70. Is electrically connected, and power can be supplied from the power source to the heat generating unit 333.

By the way, the temperature of the heating member 330 rises due to the heat generated by the heat generating portion 333, so that thermal expansion occurs. The expansion and contraction of the heating member 330 due to such a temperature change tends to be remarkable especially in the longitudinal direction of the heating member 330. Therefore, the accommodating recess 341 of the heater holder 340 in which the heating member 330 is accommodated is formed in advance larger than the heating member 330 in the longitudinal direction so that the heating member 330 can freely expand and contract in the longitudinal direction even if the temperature changes. It is necessary to secure a gap S in the direction (see FIG. 30).

However, if there is a gap S in the longitudinal direction between the heating member 330 and the accommodating recess 341, rattling of the heating member 330 in the accommodating recess 341 occurs when the heating member 330 is not thermally expanded. Then, due to this, the contact position between the electrode portion 333a and the connector 70 (contact terminal 72) may shift, causing wear or poor contact. In addition, there is a concern that the fixing quality may deteriorate due to the heat generation region of the heating member 330 changing in the longitudinal direction.

In particular, when a metal material that is cheaper than ceramic is used as the material of the base material layer 331 from the viewpoint of workability and cost reduction, the amount of expansion and contraction of the heating member 330 in the longitudinal direction due to temperature change is even larger. Therefore, it is necessary to secure a large gap S in the longitudinal direction between the heating member 330 and the accommodating recess 341. Therefore, in this case, the rattling of the heating member 330 in the accommodating recess 341 becomes larger.

Further, when the length K (see FIG. 30) of the heat generating portion 333 is set longer than the maximum paper size Wmax as in the present embodiment, the temperature rise in the non-paper-passing region becomes remarkable. The thermal expansion in that part tends to be large. Further, when the heat generating portion 333 has the PTC characteristic, when the temperature rises in the non-passing region, the resistance value of that portion rises and the amount of heat generated increases as compared with the inside of the non-passing region. Thermal expansion is promoted.

In these cases, the rattling of the heating member 330 described above becomes more serious. The thermal expansion event caused by the PTC characteristics is not limited to the pattern in which the two heat generating portions 333 are connected in series as shown in FIG. 15, for example, the heat generating portions 333 as shown in FIG. 19 are connected in parallel. Also in the pattern connected to, if it has a component Ix in which a current flows at least in the longitudinal direction, it occurs in the same manner.

That is, as shown in the enlarged view surrounded by the alternate long and short dash line in FIG. 19, when the paper P is conveyed so as to pass between the one end portion and the other end portion of one heat generating portion 333 in the width direction. A current flows from the high-temperature non-passing region 333d through which the paper P does not pass to the low-temperature paper-passing region 333c through which the paper P passes. Then, since the same as in the case of series, the amount of heat generated in the non-paper-passing region 333d increases, and thermal expansion is promoted.

Therefore, in the present embodiment, the heating member 330 is positioned in the longitudinal direction so that the heating member 330 does not rattle in the accommodating recess 341. Hereinafter, the positioning structure of the heating member 330 and the heater holder 340 will be described.

(Positioning structure between heating member and heater holder)
As shown in FIGS. 13 and 14, a positioning hole 330a as a positioning portion is provided on one end side in the longitudinal direction of the heating member 330. In the present embodiment, the positioning hole 330a is formed by a recess formed so as to be recessed in a direction (short direction) intersecting the longitudinal direction of the heating member 330.

On the other hand, the accommodating recess 341 of the heater holder 340 is provided with a positioning projection 340b as a positioning portion for fitting with the positioning hole 330a. When the heating member 330 is accommodated in the accommodating recess 341, the heating member 330 can be positioned in the longitudinal direction with respect to the heater holder 340 by fitting the positioning hole 330a with the positioning projection 340b. As a result, it becomes possible to prevent the heating member 330 from rattling in the longitudinal direction in the accommodating recess 341.

In the heating member 330 and the heater holder 340, no positioning portion is provided on the end side opposite to the end side on which the respective positioning portions (positioning holes 330a and positioning protrusions 340b) are provided. By doing so, the expansion and contraction of the heating member 330 due to the temperature change is not restricted in the longitudinal direction.

A test was conducted to confirm the effects of the heating member and the heater holder having the above-mentioned positioning portion. In the test, a heating member and a heater holder having a positioning portion and a heating member and a heater holder having no positioning portion are prepared, and each is mounted on the same fixing device and the same image forming device, and letter-sized plain paper is placed in the vertical direction. In addition, 100 sheets were passed at an output number of 50 sheets (50 ppm) per minute.

As a result, in the case where the positioning portion is not provided, the fixing defect occurs on one end side in the width direction of the paper on the second sheet after the start of paper passing, and the release layer (PFA layer) of the fixing belt is peeled off on the 50th sheet. rice field. It is considered that this is because, as shown in FIG. 20, as a result of the heating member 330 being displaced to the left side from the normal position (the position indicated by the dotted line), the heat generation distribution of the heating member 330 is also displaced to the left side and temperature unevenness occurs. ..

That is, on the right side in the belt width direction, the temperature (solid line) of the fixing belt is lower than the original temperature (dotted line), so that it is probable that fixing failure occurred on the right end side of the paper. On the other hand, on the left side in the belt width direction, on the contrary, it is considered that the temperature rise of the fixing belt becomes excessive and the surface layer of the fixing belt is peeled off.

On the other hand, in the example having the positioning portion, neither poor fixing nor damage to the fixing belt (surface layer peeling) occurred. Therefore, it was confirmed that by having the positioning portion, the positioning accuracy of the heating member with respect to the heater holder is improved, and it is possible to avoid temperature distribution unevenness such as poor fixing and belt damage.

Further, as shown in FIG. 15, in the present embodiment, since the positioning hole 330a is provided on the electrode portion 333a side in the longitudinal direction of the heating member 330, the heating member 330 is positioned with reference to the electrode portion 333a side. NS. Therefore, even if the heating member 330 thermally expands, the position of the electrode portion 333a does not easily change in the longitudinal direction of the heating member 330, so that the displacement between the electrode portion 333a and the connector 70 is effectively suppressed, and wear and poor contact are obtained. Can be prevented.

Further, as in the example shown in FIG. 21, when there are electrode portions 333a on both ends in the longitudinal direction of the heating member 330, and the number of electrode portions 333a differs between the one end side and the other end side, as much as possible. In order to suppress the displacement between many electrode portions 333a and the connector 70, it is preferable to provide the positioning holes 330a on the side where the number of electrode portions 333a is large.

Further, as in the example shown in FIG. 22, when the width of the electrode portion 333a in the longitudinal direction of the heating member 330 differs between the one end side and the other end side of the heating member 330 (L1 <L2), the shorter one. It is preferable to provide the positioning hole 330a on the electrode portion 333a side (L1 side). By doing so, it is possible to suppress the deviation between the electrode portion 333a having a small width and the connector 70, and it is possible to secure the conductivity.

From another point of view, the electrode portion 333a can be shortened in the longitudinal direction on the side where the positioning hole 330a is provided, so that the size and cost can be reduced. Further, as shown in FIG. 15, in the present embodiment, the positioning hole 330a is provided corresponding to the position of the left side feeder line 333b in the longitudinal direction of the heating member 330.

It is also possible to provide a positioning hole 330a at a location other than the left feed line 333b, for example, at a location of the heat generating portion 333 or the electrode portion 333a, but in that case, the heating member 330 (base material layer 331) is in the lateral direction. It may increase in (vertical direction in FIG. 15). In the heat generating portion 333, it is necessary to secure a width equal to or larger than a predetermined width (for example, 5 mm or more) in the lateral direction in order to supply sufficient heat to the paper, and the electrode portion 333a also considers the misalignment with the connector 70. Therefore, it is necessary to secure a width equal to or larger than a predetermined width (for example, 5 mm or more) in the lateral direction.

On the other hand, since the left feeder line 333b does not have such a situation, the width in the lateral direction can be made relatively small if energization is possible. Therefore, by providing the positioning hole 330a corresponding to the position of the left side feeder line 333b having a high degree of freedom in design to some extent, it is possible to avoid an increase in the size of the heating member 330 in the lateral direction.

FIG. 23 is an enlarged view showing the positioning hole 330a and the positioning protrusion 340b. In FIG. 23, the upper side is the front side of the heating member 330, and the lower side is the back side of the heating member 330. As shown in FIG. 23, a corner curved surface portion 340c may be formed at the root portion of the positioning protrusion 340b.

When such a corner curved surface portion 340c is present, when the positioning protrusion 340b is fitted into the positioning hole 330a, as shown in FIG. 23, the width of the positioning protrusion 340b is widened at the corner curved surface portion 23c, so that positioning is performed. The positioning projection 340b cannot be completely inserted into the hole 330a, and a gap is created between the back surface of the heating member 330 and the bottom surface of the accommodating recess 341. As a result, the heating member 330 floats from the bottom surface of the accommodating recess 341, and the heating member 330 cannot be stably held.

In order to suppress such floating of the heating member 330, as shown in FIG. 24, a wide portion of the positioning hole 330a on the opening side into which the root portion of the positioning projection 340b is inserted may be formed. In the example shown in FIG. 24, the opening width of the third insulating layer 336 on the back surface side is formed larger than the opening width of the base material layer 331 in the range of (width α) 0.1 mm or more and 5 mm or less on one side in the width direction. doing.

As a result, the root portion (corner curved surface portion 23c) of the positioning protrusion 340b is completely inserted into the positioning hole 330a, and the floating of the heating member 330 with respect to the bottom surface of the accommodating recess 341 can be suppressed. .. In the present embodiment, the heating member 330 is provided with the positioning hole 330a and the heater holder 340 is provided with the positioning protrusion 340b as the positioning portion. On the contrary, as shown in FIG. 25, the heating member 330 is provided with the positioning protrusion. By providing 330b and providing a positioning hole 340d in the heater holder 340, it is possible to position the heating member 330 and the heater holder 340 in the longitudinal direction.

However, in this case, since the outer shape of the heating member 330 becomes larger due to the provision of the positioning protrusion 340b on the heating member 330, it is disadvantageous in miniaturization. Further, when the heating member 330 is cut out from a plate-shaped member such as a metal plate, if the heating member 330 is provided with protrusions, extra material must be cut out, resulting in poor yield and high manufacturing cost. Therefore, from the viewpoint of miniaturization and cost reduction, it is preferable that the positioning portion provided on the heating member 330 is the positioning hole 330a so that the outer shape of the heating member 330 does not become large.

Further, the positioning hole 330a is not limited to the above-mentioned recess, and may be a through hole as shown in FIG. 26. The through holes penetrate from the front side to the back side of the heating member 330 in the thickness direction, and openings are formed only on the front side surface and the back side surface of the heating member 330.

That is, unlike the above-mentioned recess, the through hole is not opened in the side surface portion of the heating member 330 (the surface intersecting the front side surface or the back side surface of the heating member 330). By forming the positioning hole 330a with such a through hole, the outer shape (side surface portion) of the heating member 330 can be formed into a rectangular shape without unevenness. This makes it possible to reduce the manufacturing cost of the heating member 330.

As described above, the expansion and contraction of the heating member 330 due to the temperature change tends to be remarkable especially in the longitudinal direction of the heating member 330, but the expansion and contraction of the heating member 330 also occurs in the lateral direction. Therefore, even in the lateral direction, a gap is interposed between the heating member 330 and the accommodating recess 341.

Therefore, when the heating member 330 is accommodated in the accommodating recess 341, there is some play in the lateral direction. As described above, when the heating member 330 is accommodated in the accommodating recess 341, there is play in the lateral direction, but when the fixing belt 310 rotates, the heating member 330 is positioned in the lateral direction by the rotational force. NS.

That is, as shown in FIG. 27, when the fixing belt 310 rotates, the heating member 330 is pushed to the downstream side of the fixing belt 310 in the rotation direction Q (hereinafter, referred to as “belt rotation direction”) by the rotational force. The side surface portion 330x on the downstream side in the belt rotation direction of the heating member 330 abuts on the side surface portion 341x of the accommodating recess 341 facing the heating member 330, so that the heating member 330 is positioned in the lateral direction.

Here, in the present embodiment, as shown in FIG. 28, the positioning hole 330a of the heating member 330 and the positioning projection 340b of the heater holder 340 are provided on the side surface portions 330y and 341y on the upstream side (lower side in the drawing) in the belt rotation direction. Has been done. Therefore, in the present embodiment, the side surface portions 330x and 341x on the downstream side (upper side in the drawing) in the belt rotation direction can be formed on a straight flat surface without unevenness. As a result, when the fixing belt 310 rotates, the heating member 330 can be positioned in the lateral direction between the side surface portions 330x and 341x having no unevenness, and the positioning accuracy in the lateral direction is improved.

Further, as in the example shown in FIG. 26, when the positioning hole 330a is formed of a through hole, the side surface portions 330x and 341x on the downstream side in the belt rotation direction can be similarly formed on a straight flat surface without unevenness. can. In short, in order to improve the positional accuracy of the heating member 330 in the lateral direction, the positioning portion may be provided on a portion other than the side surface portions 330x and 341x on the downstream side in the belt rotation direction of the heating member 330 and the heater holder 340.

Further, as in the example shown in FIG. 29, on the contrary, when the positioning hole 330a and the positioning protrusion 340b are provided on the side surface portions 330x and 341x on the downstream side in the belt rotation direction, the positioning is performed by the rotation of the fixing belt 310. It is possible to reliably fit the hole 330a and the positioning protrusion 340b.

(Positioning structure between heater holder and fixing device body)
Next, the positioning structure of the heater holder 340 and the fixing device main body (device frame 360) will be described. As shown in FIGS. 13 and 14, a positioning recess 340e as a positioning portion is provided on one end side in the longitudinal direction of the heater holder 340. The heater holder 340 and the support member 364 are positioned in the longitudinal direction by fitting the fitting portion 364e of the support member 364 shown on the left side of FIGS. 13 and 14 into the positioning recess 340e.

Contrary to the present embodiment, the support member 364 may be provided with a positioning recess, and the heater holder 340 may be provided with a convex fitting portion for fitting with the positioning recess. On the other hand, the support member 364 shown on the right side of FIGS. 13 and 14 is not provided with the fitting portion 364e and is not positioned in the longitudinal direction with the heater holder 340. As a result, the expansion and contraction of the heater holder 340 in the longitudinal direction due to the temperature change is not restricted.

Further, as shown in FIG. 12, the support member 364 is assembled to both side wall portions 361a by allowing the guide groove 364a to enter along the insertion groove 28b of the side wall portion 361a. Of the two support members 364 shown in FIG. 12, the support member 364 positioned in the longitudinal direction with respect to the heater holder 340 is the support member 364 on the back side.

By assembling the support member 364 on the back side to the side wall portion 361a, the heater holder 340 is positioned in the longitudinal direction with respect to the side wall portion 361a. In this way, the side wall portion 361a and the support member 364 function as positioning portions of the fixing device main body that positions the heater holder 340 in the longitudinal direction.

The stay 350 is not positioned in the longitudinal direction with respect to the support member 364. As shown in FIG. 14, the stay 350 is provided with stepped portions 350a on both end sides thereof to regulate movement (falling off) in the longitudinal direction with respect to each of the support members 364, and each stepped portion 350a is provided with each support member. It is arranged with respect to at least one of the 364s through a longitudinal gap.

That is, the stay 350 is assembled so as to have backlash in the longitudinal direction with respect to both support members 364 so that expansion and contraction in the longitudinal direction due to a temperature change is not restricted, and is positioned with respect to one of the support members 364. Not configured to be. Subsequently, the positioning structure of the fixing device main body (device frame 360) and the image forming device main body 103 will be described.

(Positioning structure between the fixing device main body and the image forming device main body)
As shown in FIG. 12, on one end side in the longitudinal direction of the rear wall portion 362a constituting the second device frame 362, a hole portion 362c as a positioning portion for positioning the fixing device main body with respect to the image forming device main body 103 is provided. It is provided. When the fixing device main body is attached to the image forming device main body 103, the protrusion 101 as a positioning portion provided on the image forming device main body 103 is inserted into the hole portion 362c of the rear wall portion 362a to form a protrusion 101. The hole portion 362c is fitted, and the fixing device main body is positioned in the longitudinal direction (belt width direction) with respect to the image forming device main body 103.

Contrary to the present embodiment, the fixing device main body may be provided with a protrusion as a positioning portion, and the image forming device main body 103 may be provided with a hole for fitting the protrusion. Further, the hole portion as the positioning portion may be a through hole or a recess having a bottom portion.

Further, the positioning portion is not provided on the end side opposite to the end side where the hole portion 362c of the rear wall portion 362a is provided. As a result, the expansion and contraction of the fixing device main body in the longitudinal direction due to the temperature change is not restricted.

As described above, in the present embodiment, the positioning in the longitudinal direction is performed between the heating member and the heater holder, between the heater holder and the fixing device main body, and between the fixing device main body and the image forming device main body, respectively. NS. Hereinafter, the positional relationship between these positioning portions will be described. Further, in the following description, the positioning portion between the heating member and the heater holder is the "first positioning portion", the positioning portion between the heater holder and the fixing device main body is the "second positioning portion", and the fixing device main body and the image forming device main body. The positioning unit with the above will be referred to as a "third positioning unit".

(Positional relationship between positioning parts)
FIG. 30 is a schematic view of the fixing device 300 disassembled. In FIG. 30, the fixing belt 310 is not shown. As shown in FIG. 30, the first positioning portion A (positioning hole 330a and positioning protrusion 340b), the second positioning portion B (positioning recess 340e and fitting portion 364e), and the third positioning portion C (hole). The portions 362c and the protrusions 101) are both provided on the same side (left side in FIG. 30) with reference to the central portion M of the heat generating portion 333 in the longitudinal direction of the heating member 330.

By providing the positioning portions A, B, and C on the same side in this way, the relative positional accuracy of the heating member 330, the heater holder 340, and the fixing device main body (device frame 360) is improved. That is, even if the heating member 330, the heater holder 340, and the fixing device main body thermally expand, they expand and contract based on the same end side (positioned end side), so that the reference end side is used. It is possible to suppress the relative misalignment of.

In particular, in the present embodiment, the position of the first positioning portion A and the position of the second positioning portion B in the longitudinal direction of the heating member 330 are the same positions (positions that overlap in the longitudinal direction). , The positional accuracy of the heating member 330 and the heater holder 340 with respect to the left side wall portion 361a in FIG. 30 is improved. Therefore, on the side of the end to be positioned, the position accuracy of the heat generating portion 333 with respect to the paper can be improved, and the fixability can be improved.

Further, as shown in FIG. 30, the thermistor TH as a temperature sensor for detecting the temperature of the fixing belt also has the positioning portions A, B, and C with reference to the central portion M of the heat generating portion 333 in the longitudinal direction of the heating member 330. By providing it on the same side, the positional accuracy of the thermistor TH with respect to the heating member 330 can also be improved. As a result, the temperature of the fixing belt 310 based on the detection result of the thermistor TH can be controlled with high accuracy.

The temperature sensor that detects the temperature of the fixing belt may be either a contact type or a non-contact type. Further, instead of detecting the temperature of the fixing belt, it is also possible to use a temperature sensor that detects the temperature of the pressure roller 320. When the temperature sensor is arranged in contact with or close to the back surface of the heating member 330, an insulating layer (third insulating layer 336) may be provided on the back surface of the base material layer 331 as in the present embodiment. desirable.

Further, as shown in FIG. 31, when papers P1, P2, and P3 having different width sizes are supplied with one end (left end side in the drawing) in each width direction aligned as the positioning reference G, the paper is positioned. It is desirable that the reference G is also provided on the same side as the positioning portions A, B, and C with reference to the central portion M of the heat generating portion 333. As a result, the position accuracy of the paper with respect to the heating member 330 is improved, and the fixing quality can be improved.

In the present embodiment, all of the positioning portions A, B, and C are provided on the same side, but it is possible to improve the positioning accuracy by providing only two of these on the same side. be. For example, only the first positioning unit A and the second positioning unit B, or only the first positioning unit A and the third positioning unit C are arranged on the same side with respect to the central portion M of the heat generating portion 333. You may. Subsequently, the positional relationship between the first positioning unit A and the drive transmission gear 324 of the pressure roller 320 will be described.

(Positional relationship between the first positioning unit and the drive transmission gear)
As shown in FIG. 30, in the present embodiment, in order to avoid interference of the heating member 330 and the heater holder 340 with the drive transmission gear 324, the first positioning portion A and the drive transmission gear 324 are positioned at the center of the heat generating portion 333. They are provided on opposite sides of each other with reference to M. On the other hand, if the first positioning portion A and the drive transmission gear 324 are provided on the same side, the heating member 330 and the heater holder 340 may interfere with the drive transmission gear 324.

That is, when the positioning portion A is provided on the heating member 330 and the heater holder 340, the heating member 330 and the heater holder 340 become longer by the installation space of the first positioning portion A, so that the respective ends reach the position of the drive transmission gear 324. When extended, there is a problem of interfering with the drive transmission gear 324. Further, if the diameter of the drive transmission gear 324 is small, the force received from the gear on the image forming apparatus main body 103 side becomes large, and the rotation shaft of the pressurizing roller 320 may bend. Therefore, the diameter of the drive transmission gear 324 Is desirable.

However, if the diameter of the drive transmission gear 324 is increased, interference with the heating member 330 and the heater holder 340 is more likely to occur. Further, when the heating member 330 is held on the surface of the heater holder 340 on the pressure roller 320 side (nip portion N side) as in the present embodiment (see FIG. 2), the heating member 330 and the drive transmission gear 324 As the distance becomes closer, these interferences are more likely to occur.

As a measure to avoid such interference, for example, a method of extending the shaft of the pressurizing roller 320 and arranging the drive transmission gear 324 so as not to interfere with the heating member 330 or the heater holder 340 can be considered. However, when the shaft of the pressure roller 320 is extended, the rigidity (flexural strength) with respect to the pressing force between the pressure roller 320 and the fixing belt 310 is lowered, and bending is likely to occur.

Therefore, it becomes necessary to form the rotating shaft thick so as to secure the rigidity of the pressure roller 320, which causes another problem such as an increase in weight and an increase in cost. Therefore, the method of extending the shaft of the pressure roller 320 is not a preferable solution.

Therefore, in the present embodiment, as described above, the first positioning portion A and the drive transmission gear 324 are provided on opposite sides of each other with respect to the central portion M of the heat generating portion 333. By providing the first positioning portion A and the drive transmission gear 324 on opposite sides in this way, the heating member 330 and the heater holder 340 interfere with the drive transmission gear 324 without extending the shaft of the pressure roller 320. Will be able to be avoided.

Further, as shown in FIG. 30, the electrode portion 333a is also provided on the side opposite to the drive transmission gear 324 with reference to the central portion M of the heat generating portion 333, so that the electrode portion 333a is generated by the heat generated in the meshing portion of the gear. And the connector 70 connected to the connector 70 can be suppressed from rising in temperature. This makes it possible to prevent a decrease in contact pressure with respect to the electrode portion 333a due to an increase in the temperature of the connector 70.

From the viewpoint of miniaturization and cost reduction of the heating member 330, as described above, the positioning portion provided on the heating member 330 is not the positioning projection 330b shown in FIG. 17, but the positioning hole 330a shown in FIG. Is preferable. However, if the positioning portion is provided on the heating member 330 and the heater holder 340 in any case, it is necessary to lengthen them, so that the problem of interference between the heating member 330 and the heater holder 340 with respect to the drive transmission gear 324 may occur as well.

Therefore, from the viewpoint of avoiding interference with the drive transmission gear 324 by providing the positioning portion on the heating member 330 and the heater holder 340, the positioning portion provided on the heating member 330 is any one of a concave portion, a convex portion, and a through hole. It is not limited to. Further, the drive transmission member provided on one end side of the pressure roller 320 may be a drive transmission gear 324, a pulley for tensioning the drive transmission belt, a coupling mechanism, or the like. Subsequently, a configuration for suppressing heat transfer to the electrode portion 333a of the heating member 330 will be described.

(Heat transfer suppression structure to the electrode part)
In the above description, the configuration in which the heating member 330 is provided with the positioning hole 330a in order to position the heating member 330 in the longitudinal direction has been described, but such a positioning hole 330a is provided with the heat generating portion 333. By forming it between the portion and the portion where the electrode portion 333a is provided, it can be used as a means for suppressing heat transfer from the heat generating portion 333 to the electrode portion 333a. That is, as shown in FIG. 15, the portion provided with the positioning hole 330a is a small cross-sectional portion 330z having a smaller cross-sectional area than the portion provided with the heat generating portion 333. It is possible to suppress heat transfer from the heat generating portion 333 to the electrode portion 333a.

As a result, the temperature rise of the connector 70 in contact with the electrode portion 333a can be suppressed, and the decrease in the contact pressure with respect to the electrode portion 333a due to the temperature rise of the connector 70 can be prevented. As described above, according to the present embodiment, even if the heat generating portion 333 generates heat, the temperature of the electrode portion 333a and the connector 70 is less likely to rise, and the contact pressure of the connector 70 with respect to the electrode portion 333a can be maintained satisfactorily. Therefore, reliability is improved.

In particular, as in the present embodiment, when the length of the heat generating portion 333 is set longer than the maximum paper size, or when the heat generating portion 333 has PTC characteristics, the heating member 330 is formed in at least a part of the heat generating portion 333. When the current is configured to flow in the longitudinal direction of the paper, the amount of heat generated increases in the non-paper-passing region, so that the effect of providing such a small cross-sectional portion 330z can be greatly expected.

Further, in the case of the configuration of the present embodiment, the positioning hole 330a also functions as a small cross-sectional portion 330z that suppresses heat transfer from the heat generating portion 333 to the electrode portion 333a, thereby forming the positioning portion and the heat transfer suppressing portion. It is not necessary to provide them separately, and the heating member 330 can be downsized. Further, since heat transfer to the electrode portion 333a can be suppressed only by forming the small cross-sectional portion 330z on the heating member 330, it is not necessary to newly add another member such as a heat radiating member to the heating member 330, which is advantageous for miniaturization. Is.

Further, the small cross-sectional portion 330z can be formed into an arbitrary shape as long as the cross-sectional area is smaller than the portion provided with the heat generating portion 333. For example, it is possible to form the small cross-sectional portion 330z by providing the positioning hole 330a formed of the through hole as in the example shown in FIG. 26.

Further, as in the example shown in FIG. 32, the small cross-sectional portion 330z is formed by partially thinning the base material layer 331 between the portion provided with the heat generating portion 333 and the portion provided with the electrode portion 333a. It is also possible to form. Hereinafter, the configurations of other fixing devices will be described.

(Configuration of other fixing devices)
In the example shown in FIG. 33, contrary to the above-described embodiment, the drive transmission gear 324 is provided on the same side as the positioning portions A, B, and C with reference to the central portion M of the heat generating portion 333. In this case, since the position accuracy of the drive transmission gear 324 is improved, the meshing with the gear provided in the image forming apparatus main body 103 can be performed with high accuracy, and the reliability regarding durability is improved.

Further, in the example shown in FIG. 33, the third positioning portion C for positioning the fixing device main body (device frame 360) and the image forming device main body 103 is arranged with the end portion 361e of one side wall portion 361a of the fixing device 300. It is composed of a hole 102 (or a recess) on the image forming apparatus main body 103 side to be fitted with the hole 102 (or a recess). In this case, all of the positioning portions A, B, and C can be set to the same position (overlapping positions in the longitudinal direction) in the longitudinal direction of the heating member 330. By setting all of the positioning portions A, B, and C at the same position in the longitudinal direction of the heating member 330 in this way, the positional accuracy of the heating member 330 with respect to the image forming apparatus main body 103 is further improved.

Further, as in the example shown in FIG. 34, the edge of the insertion groove 361d of the side wall portion 361a may be directly fitted to the hole portion 330c (small cross-sectional portion 330z) as the positioning portion provided in the heating member 330. Alternatively, as in the example shown in FIG. 35, the protrusion 350b provided on the stay 350 is directly fitted to the hole 330c (small cross-sectional portion 330z) provided on the heating member 330 to fit the heating member 330. Can also be positioned in the longitudinal direction. In this way, the mating member that fits into the positioning portion of the heating member 330 and performs positioning may be the side wall portion 361a or the stay 350 in addition to the heater holder 340 described above.

Moreover, in this case, the heat of the heating member 330 is easily transferred to the side wall portion 361a and the stay 350 that are in direct contact with the heating member 330, so that the temperature rise of the heating member 330 can be suppressed. Further, as shown in FIGS. 34 and 35, the portion where the side wall portion 361a and the stay 350 come into direct contact with the heating member 330 is located between the heat generating portion 333 and the electrode portion 333a in the longitudinal direction of the heating member 330. By providing this, heat transfer from the heat generating portion 333 to the electrode portion 333a can be further suppressed.

Further, by forming the material of the side wall portion 361a and the stay 350 with a material having a higher thermal conductivity than the heater holder 340, more preferably a material having a higher thermal conductivity than the heating member 330 (base material layer 331), heating is performed. The temperature rise of the member 330 can be efficiently suppressed. However, if the heat of the heating member 330 is easily transferred to the side wall portion 361a and the stay 350 on the one end side in the longitudinal direction thereof, the difference in the amount of heat radiation from the opposite end side becomes large, so that the heating member 330 There is a possibility that the temperature will be non-uniform between the one end side and the other end side.

As a countermeasure against this, for example, as shown in FIG. 36, heat is conducted more than the base material layer 331 on the end side opposite to the end where the hole 330c (small cross section 330z) of the heating member 330 is provided. It is preferable to provide the high thermal conductivity member 74 having a high rate. As a result, the heat transfer effect (heat dissipation effect) is increased even on the end side opposite to the end side where the side wall portion 361a and the stay 350 are in direct contact with each other. It is possible to alleviate the temperature non-uniformity between the side and the side.

Further, in order to effectively alleviate the temperature non-uniformity, the distance E1 from the central portion M of the heat generating portion 333 to the hole portion 330c and the distance E2 from the central portion M of the heat generating portion 333 to the high heat conductive member 74 are set. The difference should be 2 mm or less, preferably the same distance (symmetrical position). Further, the high heat conductive member 74 may be formed in a leaf spring shape or the like so that the high heat conductive member 74 also functions as a holding member that holds the heating member 330 and the heater holder 340 together. As a result, the two functions of soaking the heat of the heating member 330 and preventing it from falling off can be realized with one component, and the cost can be reduced.

Further, the present invention can be applied to the fixing device as shown in FIGS. 37 to 39 in addition to the fixing device described above. Hereinafter, the configurations of the fixing devices shown in FIGS. 37 to 39 will be briefly described.

First, in the fixing device 300 shown in FIG. 37, a pressing roller 370 is arranged on the side opposite to the pressing roller 320 side with respect to the fixing belt 310, and the fixing belt 310 is formed by the pressing roller 370 and the heating member 330. It is configured to heat by sandwiching. On the other hand, on the pressure roller 320 side, the nip forming member 380 is arranged on the inner circumference of the fixing belt 310. The nip forming member 380 is supported by the stay 350, and the nip forming member 380 and the pressure roller 320 sandwich the fixing belt 310 to form the nip portion N.

Next, in the fixing device 300 shown in FIG. 38, the above-mentioned pressing roller 370 is omitted, and in order to secure the circumferential contact length between the fixing belt 310 and the heating member 330, the heating member 330 is the fixing belt 310. It is formed in an arc shape according to the curvature of. Others have the same configuration as the fixing device 300 shown in FIG. 37.

Finally, in the fixing device 300 shown in FIG. 39, a pressure belt 390 is provided in addition to the fixing belt 310, and the heating nip (first nip portion) N1 and the fixing nip (second nip portion) N2 are separately configured. doing. That is, the nip forming member 380 and the stay 381 are arranged on the side opposite to the fixing belt 310 side with respect to the pressure roller 320, and the pressure belt 390 is rotated so as to include the nip forming member 380 and the stay 381. Arranged as possible.

Then, the paper P is passed through the fixing nip N2 between the pressure belt 390 and the pressure roller 320, heated and pressed to fix the image. Others have the same configuration as the fixing device 300 shown in FIG.

(Application to heat rollers for electrophotographic printers)
The present invention can also be applied to the heat roller of the electrophotographic printer 400 shown in FIG. 40. The electrophotographic printer 400 uses a plurality of heat rollers such as a paper moisture removing roller 430. The heat roller can be configured by sandwiching a cylindrical planar heating element having the above-mentioned heat block between a double pipe composed of an inner pipe and an outer pipe.

The electrophotographic printer 400 of FIG. 40 has a photoconductor drum 410 and a fixing flash lamp 420. The heat roller is used as a paper moisture removing roller 430 arranged on the upstream side of the photoconductor drum 410. Further, the heat roller is used as a drum dew condensation prevention roller 440 arranged inside the photoconductor drum 410. Further, the heat roller is used as a preheat roller 450 arranged between the photoconductor drum 410 and the fixing flash lamp 420. Further, the heat roller is used as a paper wrinkle smoothing roller 460 arranged on the downstream side of the fixing flash lamp 420.

In this way, the heat roller (a) removes moisture from the paper before transfer, (b) prevents dew condensation on the photoconductor drum, (c) preheats before flash fixing, and (d) media after fixing. Can be used to smooth out wrinkles. Of course, the heat roller need not be used in all of the above examples. Further, the application of the heat roller is not limited to the example shown in FIG. 40. Since the resistance of the heat block can be easily set by providing a conductor or a high resistor in the resistor, versatility other than the fuser is also enhanced.

Although the configurations of various fixing devices have been described above, the heating device according to the present invention includes a heat roller type fixing device in which a heating member is arranged on the inner circumference in addition to a type fixing device that directly heats a thin-walled fixing belt. It is also applicable to. Further, the heating device according to the present invention is not applied only to the fixing device. For example, the heating device according to the present invention can be applied to a drying device mounted on an inkjet image forming device and a heating member of an inkjet print head in order to dry the ink applied to the paper.

Further, in the heating device according to the present invention, a high resistor having a resistance larger than that of the resistor may be provided instead of the conductor provided in the resistor. That is, instead of reducing and adjusting the resistance by the resistor conductor laminated portion, the resistance is increased and adjusted by the resistor high resistor laminated portion.

Further, the heating member according to the present invention can also be applied to a coating device (laminator) that thermocompression-bonds a film as a coating member to the surface of the sheet while transporting a sheet such as paper by a belt member. Further, the heating member according to the present invention is applicable not only to the belt heating device for heating the belt member but also to the heating device not provided with the belt member. Further, the resistor of the heating member can be formed in any shape such as a sheet shape, a meandering shape, a comb tooth shape, and a spiral shape.

1Y, 1M, 1C, 1Bk: Image drawing unit 2: Photoreceptor (image carrier)
3: Charging device 4: Developing device 4a: Developer carrier 5: Cleaning device 5a: Cleaning blade 6: Exposure device 7: Paper feeding device 8: Transfer device 10: Paper ejection device 11: Intermediate transfer belt 12: Primary transfer roller 13: Secondary transfer roller 14: Paper transport path 15: Timing roller 50: Paper feeder 51, 53, 54: Insulation layer 55: High heat conductive layer 60: Paper feed roller 70: Connector 71: Housing 72: Contact terminal 72a : Contact portion 73: Harness 74: High heat conductive member 100: Image forming apparatus 101: Projection 102: Hole portion 103: Image forming apparatus main body 250: Resist roller pair 300: Fixing device 310: Fixing belt 320: Pressurizing roller 321: Core Gold 322: Elastic layer 323: Release layer 324: Drive transmission gear 330: Heating member 331: Base material layer 332, 335, 336: Insulation layer 333: Heat generating part 333a, 339a to 339c: Electrode part 333b, 339d to 339f: Power supply line 333c: Paper-passing area 333d: Non-paper-passing area 334: Conductor layer 337: Heat block 337a: Central heat block 337b: Both ends heat block 338: Resistance adjustment unit 340: Heater holder 350: Stay 360: Equipment frame 363: Bearing 364: Support member 365: Spring 370: Pressing roller 380: Nip forming member 381: Stay 390: Pressurized belt P: Paper TH: Thermista TM: Transfer means

Japanese Patent No. 45122232 JP-A-2017-191149

Claims (15)

A base material having a longitudinal direction, a plurality of resistors directly or indirectly arranged on the base material, and a conductor having a smaller electric resistance than the resistor directly or indirectly arranged on the base material. In a heating device having a heating member having an insulating member covering the resistor and heat transfer to the member to be heated through one surface of the heating member.
At least one of the plurality of resistors has a resistor conductor laminated portion in which the resistor and the conductor overlap, and a surface having a surface accuracy higher than a predetermined range of flatness including the resistor conductor laminated portion. Is provided on one surface of the heating member. A base material having a longitudinal direction, a plurality of resistors directly or indirectly arranged on the base material, and a conductor having a smaller electric resistance than the resistor directly or indirectly arranged on the base material. In a heating device having a heating member having an insulating member covering the resistor and heat transfer to the member to be heated through one surface of the heating member.
At least one of the plurality of resistors has a resistor conductor laminated portion in which the resistor and the conductor are overlapped, and the plurality of resistors including the resistor conductor laminated portion are formed on one surface of the heating member. A heating device characterized in that a surface having a surface accuracy higher than the flatness of a predetermined range including the resistor conductor laminated portion is provided on one surface of the heating member while being arranged on a surface different from the above. The heating device according to claim 1 or 2, wherein the end portion of the resistor conductor laminated portion in the longitudinal direction of the base material is located at the center of the predetermined range. The heating device according to claim 3, wherein the predetermined range is a circular shape having a diameter of 3 mm or more and 15 mm or less. Among the plurality of resistors, the resistor having a longer current flow path has a longer total length along the current flow path than the resistor having a shorter current flow path. The heating device according to any one of claims 1 to 4, wherein a body conductor laminated portion is provided. Among the plurality of resistors, the length of the path of the resistor having the longest current flow path is L1, the width is D1, the width of the longest resistor in the longitudinal direction is l1, and the other resistors. When the length of the path is L2, the width is D2, and the width of the other resistor in the longitudinal direction is l2.
l1> l2 and L1 / D1 <L2 / D2 ... (Equation 1)
The heating device according to any one of claims 1 to 5, wherein the resistor conductor laminated portion is provided so as to satisfy the above conditions. There are three or more power supply units that supply power to the resistor, and the plurality of resistors include a first resistor that generates heat by conducting two power supply units among the three or more power supply units.
A second resistor that generates heat by conducting at least one of the two feeding parts with a feeding part other than the two feeding parts, and a second resistor.
The heating device according to any one of claims 1 to 6. The heating device according to any one of claims 1 to 7, wherein the plurality of resistors are formed by folding back. Claim that at least one or more resistors among the plurality of resistors have a set of resistor conductor laminated portions and a conductor portion sandwiched between the set of resistor conductor laminated portions. The heating device according to any one of 1 to 8. The heating device according to any one of claims 1 to 9, wherein the width of the resistor conductor laminated portion in the lateral direction orthogonal to the longitudinal direction of the base material is made larger than the width of the resistor in the lateral direction. .. A base material having a longitudinal direction, a plurality of resistors directly or indirectly arranged on the base material, and a conductor having a smaller electric resistance than the resistor directly or indirectly arranged on the base material. In a heating device having a heating member having an insulating member covering the resistor and heat transfer to the member to be heated through one surface of the heating member.
At least one of the plurality of resistors has a resistor high resistor laminated portion in which the resistor is provided with a high resistor having a resistance larger than that of the resistor, and includes the resistor high resistor laminated portion. A heating device characterized in that a surface having a surface accuracy higher than a predetermined range of flatness is provided on one surface of the heating member. A base material having a longitudinal direction, a plurality of resistors directly or indirectly arranged on the base material, and a conductor having a smaller electric resistance than the resistor directly or indirectly arranged on the base material. In a heating device having a heating member having an insulating member covering the resistor and heat transfer to the member to be heated through one surface of the heating member.
At least one of the plurality of resistors has a resistor high resistor laminated portion in which the resistor is provided with a high resistor having a resistance larger than that of the resistor, and includes the resistor high resistor laminated portion. The plurality of resistors are arranged on a surface different from one surface of the heating member, and a surface having a surface accuracy higher than the flatness of a predetermined range including the resistor high resistor laminated portion is provided on one surface of the heating member. A heating device characterized in that it is installed in. The heating device according to any one of claims 1 to 12, wherein the material of the base material is a metal such as stainless steel, iron, or aluminum, ceramic, or glass. A flexible sleeve-shaped rotating member and
The heating device according to any one of claims 1 to 12, wherein the heating member transfers heat to the inner circumference of the rotating member.
It has a pressure member that sandwiches the rotating member and press-contacts the heating member to form a nip portion between the rotating member and the heating member.
A fixing device characterized in that heat of the heating member is applied to the paper when the paper is sandwiched and conveyed by the nip portion. An image forming apparatus including a paper feeding device, an image forming unit, a transfer device, and a fixing device according to claim 14.

Images