JP2021131475A - Heater member, heating device, fixing device, and image forming apparatus - Google Patents

Abstract

To detect temperatures of heat blocks having resistance adjustment units with temperature detection members in such a manner to avoid the occurrence of an error.SOLUTION: A heater member 330 has: a plurality of heat blocks 331a to 331d, 332 that have resistors that generate heat upon energization and are formed on a surface of a substrate 360; resistance adjustment units 338 that have an electric resistance smaller than the electric resistance of the resistors and are formed on energization paths of the heat blocks; and temperature detection members (thermistors TH1 to TH4) that are disposed to be able to detect temperatures of the heat blocks. The temperature detection members TH1 to TH4 are disposed at positions separated from the resistance adjustment units 338.SELECTED DRAWING: Figure 3A

Description

The present invention relates to a heater member, a heating device, a fixing device, and an image forming device, and in particular, a heater member having a heat block composed of a resistor that generates heat when energized, and a heating device, a fixing device, and an image using the heater member. Regarding the forming device.

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 heater member. This heater member is composed of a heater base material and a resistance heating element (planar heater). A pressure roller as a pressure member is arranged on the outside of the fixing belt, and the fixing nip is formed by crimping the pressure roller to the heater member with the fixing belt sandwiched between them.

The planar heater is formed on the heater substrate by screen printing using a conductive paste. The resistance pattern of the planar heater ranges from a simple one-reciprocating or one-pass series connection in the longitudinal direction of the heater substrate, to a plurality of heat blocks having a meandering resistance pattern connected in parallel in the longitudinal direction of the heater substrate. There is something. 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.

In the heat block, it is desirable to form the resistance wire of the resistance pattern with the same resistance paste with a constant width, a constant thickness, and a constant meandering number in order to make the heat generation density uniform and to improve the efficiency and cost of screen printing. Furthermore, due to the need to set the division position of the heat blocks according to the paper size, the longitudinal length of each heat block cannot be set to the length obtained by simply dividing the maximum paper size by the number of blocks. be.

Therefore, normally, the longitudinal length L1 of the plurality of heat blocks HB1 on the central side is set longer than the longitudinal length L2 of the heat blocks HB2 on both ends (L2 <L1). Therefore, although the heat block HB1 on the center side has a larger heat generation area in block units, the resistance value R1 of the heat block HB1 is larger than the resistance value R2 of the heat block HB2 (R2 <R1), and the common voltage. Alternatively, when duty is supplied, the heat generation density on both ends becomes considerably higher than that on the center side. There is also a method of supplying different voltages or duties to the heat blocks on the center side and both ends to make the heat generation density uniform, but this complicates the power supply and control and increases the cost.

Therefore, as one of the solutions to make the heat generation density in the longitudinal direction of the heater member uniform, a resistor made of a material having a resistance value smaller than that of the resistor of the heat block is applied to the energization path of the heat block having the longer energization path. It is conceivable to partially form the adjusting portion.

On the other hand, a temperature detection member (thermistor) is arranged in each heat block for temperature control. However, when the temperature detection member is arranged in the heat block provided with the resistance adjusting unit as described above, the arrangement position thereof. Depending on the detection temperature, an error may occur. That is, since the resistance adjusting unit has a low resistance and a low heat generation density, if the temperature detecting member is arranged close to the resistance adjusting unit, a temperature lower than the temperature that should be originally detected is detected. If the temperature is controlled at this low detected temperature, the temperature of the heat block becomes higher than the target temperature, and there is a risk of abnormal images such as hot offset and gloss abnormality.

The present invention has been made in view of such a situation, and an object of the present invention is to detect the temperature of a heat block having a resistance adjusting portion with a temperature detecting member so as not to cause an error.

In order to solve the above problems, the heater member of the present invention has a heat block having a resistor that generates heat when energized and formed of a plurality of heat blocks on the surface of the base material, and an electric resistance smaller than the electric resistance of the resistor. A position having a resistance adjusting unit formed in the energization path of the heat block and a temperature detecting member arranged so as to be able to detect the temperature of the heat block, and the temperature detecting member separated from the resistance adjusting unit. It is characterized in that it is arranged in.

According to the present invention, the temperature of the heat block having the resistance adjusting portion can be detected by the temperature detecting member so as not to cause an error.

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 dual type heater member which arranged the thermistor on the upstream side of a resistance adjustment part. It is a top view of the dual type heater member which arranged the thermistor on the downstream side of a resistance adjustment part. It is a top view of the heat block in which the thermistor is superposed on the resistance adjustment part. (A) to (f) are plan views of the heat block showing a plurality of arrangement examples of the resistance adjusting unit and the thermistor. It is a top view of the single type heater member which arranged the thermistor on the downstream side of a resistance adjustment part. (A) to (f) are plan views of the heat block showing a plurality of arrangement examples of the resistance adjusting unit and the thermistor. It is a top view of the dual type heater member in which the end portions adjacent to each other of a heat block are inclined and overlapped in the lateral direction. It is a figure which shows the structure of another fixing device. It is a figure which shows the structure of still another fixing device. It is a figure which shows the structure of still another fixing device.

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 copying machine, a facsimile, or a multifunction device thereof, in addition to a printer.

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 output 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.

The fixing device 300 is arranged on the downstream side of the transfer nip N. The fixing device 300 rotates while abutting the fixing belt 310 as a fixing member heated by the heat blocks 331a to 331d and 332 described later as a heating element described later and the fixing belt 310 at a predetermined pressure. A pressure roller 320 as a member is provided.

(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 heater member 330 for heating the fixing belt 310. The heater member 330 is held by the heater holder 344, and the heater holder 344 is reinforced in the longitudinal direction by a stay 350 as a reinforcing member.

The fixing belt 310 is composed of a flexible sleeve-shaped rotating member, and has, for example, a tubular 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 fluorine-based resin such as PFA or PTFE in order to enhance durability and ensure mold releasability.

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 heater 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 heater 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 heater member 330 in direct contact with the fixing belt 310. The heat transfer efficiency to the fixing belt 310 is improved.

Further, the heater 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 heater member 330, the fixing quality may deteriorate. Therefore, the heater member 330 Should be in contact with the inner peripheral surface of the fixing belt 310.

The heater member 330 includes a base material layer 330a, a conductor layer 330d having a first insulating layer 330b, a heat generating portion 330c, and a second insulating layer 330e, which are sequentially laminated on the nip portion N side of the base material layer 330a. It is composed of a third insulating layer 330f laminated on the opposite side of the layer 330a.

The base material layer 330a 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 330b, 330e, 330f, the conductor layer 330d is formed by the deviation between the base material layer 330a and the insulating layers 330b, 330e, 330f 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 330a.

The heater holder 344 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 344 opposite to the heater member 330 side is supported by the stay 350, the heater member 330 and the heater holder 344 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 344 tends to be heated to a high temperature by the heat of the heater member 330, it is desirable that the heater holder 344 is made of a heat-resistant material. For example, when the heater holder 344 is made of a heat-resistant resin having low thermal conductivity such as LCP or PEEK, heat transfer from the heater member 330 to the heater holder 344 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 pressure roller 320 functions as a drive 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 be driven to rotate with the rotation of the pressure roller 320. During rotation, the fixing belt 310 slides with respect to the heater 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 heater 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 heater 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.

(Heater member)
As shown in FIG. 3A, the heater member 330 has a total of six heat blocks, four heat blocks 331a to 331d on the central side and two heat blocks 332 on both end sides. The heat blocks 331a to 331d and 332 are formed on the surface of the heater base material 360 in a resistance pattern having a constant width, a constant thickness and a constant meandering number, and are parallel to the electrode portions 333 to 335 described later by feeder lines 351 to 355. Connected to.

The adjacent ends of the heat blocks 331a to 331d and 332 have a straight shape in the lateral direction. For this reason, there is a small gap extending in the lateral direction between the blocks, but by providing a heat equalizing member with good thermal conductivity on the base material 360 of the heat blocks 331a to 331d and 332, the temperature unevenness in the fixing belt 310 is eliminated. can do.

Two electrode portions 333 and 334 are formed at one end of the heater member 330, and one electrode portion 335 is formed at the other end. The electrode portion 333 is connected to one end in the lateral direction (upper end in FIG. 3A) of the central heat blocks 331a to 331d by a conductive wire 336, and the other end in the lateral direction of the central heat blocks 331a to 331d (lower end in FIG. 3A). The electrode portion 335 on the opposite side is connected to the conductive wire 341 by a conductive wire 341.

On the other hand, one end (upper end in FIG. 3A) of the heat block 332 on both ends is connected to the electrode 334 on the left side by the conductive wire 339, 340, and the other end (lower end in FIG. 3A) of the heat block 332 on both ends connects the conductive wire 341. It is connected to the electrode 335 via.

The electrode portion 333 is connected to the power supply PW by the feeder line 354, the switch SW1, and the feeder lines 355 and 352. The electrode portion 334 is connected to the power supply PW by a feeder line 351, a switch SW2, and a feeder line 352. The electrode portion 335 on the opposite side is connected to the power supply PW by a feeder line 353.

The switch SW1 and the switch SW2 are arranged in parallel, and the heat block 331 on the center side and the heat block 332 on both ends can be independently switched on and off. That is, the heater member 330 is configured as a dual type heater member capable of independently controlling the heat blocks on the center side and both ends.

For the meandering resistance pattern of the heat blocks 331a to 331d and 332, 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 coated. It can be formed by firing 331. In addition to these, a resistance material of silver alloy (AgPt) or ruthenium oxide (RuO ₂ ) may be used as the material of the resistance pattern.

The conductive wires 336, 339, 340, and 341 are composed of conductors having a resistance value smaller than that of the resistance patterns of the heat blocks 331a to 331d and 332. As the material of the conductive wire 336, 339, 340, 341 and the electrode portions 333 to 335, silver (Ag) or silver palladium (AgPd) can be used, and the conductive wire 336 is produced by screen printing such a material. 339, 340, 341 and electrode portions 333 to 335 are formed.

The boundary (division position) between the heat blocks 331a to 331d on the center side and the heat blocks 332 on both ends is set according to the paper size. That is, for example, the central side heat blocks 331a to 331d are arranged corresponding to the case of vertically transporting A4 paper (width 210 mm), and for example, the central side corresponding to the case of vertically transporting A3 paper (width 297 mm). Heat blocks 331a to 331d and heat blocks 332 on both ends are arranged.

Specifically, four central heat blocks 331a to 331d 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 heater member 330. The length of each heat block 331a to 331d can be, for example, 51 mm (51 mm × 4 = 214 mm> 210 mm).

Further, the central side heat blocks 331a to 331d and the both end side heat blocks 332 are arranged in accordance with the case where the A3 paper (width 297 mm) is vertically conveyed with reference to the central portion in the longitudinal direction of the heater member 330. The length of the heat blocks 332 on both ends can be, for example, 42 mm. (42 mm x 2 + 214 mm = 298 mm> 297 mm).

When the heat blocks 331a to 331d and 332 are connected in parallel, the resistance value (heat generation amount) per block must be increased by the number of blocks. For example, when the total resistance of 10Ω is realized by 6 blocks as shown in FIG. 3A, the resistance value of one heat block is 60Ω. In order to increase the resistance of the heat block in this way, the resistance pattern is meandered to lengthen the energization distance.

As described above, if the length of the heat block is 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, the same meandering state (constant width, constant thickness and constant number of meandering). When the heat blocks 331a to 331d and 332 are configured by the resistance pattern of, the resistance value of the central heat blocks 331a to 331d becomes larger than the resistance value of the heat blocks 332 on both ends.

Then, when the current is supplied from the common AC power supply to the heat blocks on the center side and the heat blocks on both ends with the same duty, the heat generation densities of the center heat blocks 331a to 331d become smaller than the heat generation densities of the heat blocks 332 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 heater member 330 according to the embodiment of the present invention, in order to reduce the resistance value of the central heat blocks 331a to 331d having a relatively large resistance value, the resistance of the central heat blocks 331a to 331d is adjusted as shown in FIG. It was decided to provide a part 338. The resistance adjusting unit 338 is composed of a conductor having an electric resistance smaller than that of the resistors forming the resistance patterns of the heat blocks 331a to 331d. As the material of the resistance adjusting unit 338 or the conductor, for example, silver (Ag) or silver palladium (AgPd) can be used.

By partially providing the resistance adjusting portions 338 in the central heat blocks 331a to 331d, the current paths of the heat blocks 331a to 331d are short-circuited at the portion of the resistance adjusting portions 338, and the substantial energization paths of the heat blocks 331a to 331d are short-circuited. The length can be reduced and the resistance value can be reduced. Then, the width, length or thickness of the resistance adjusting portion 338 is formed corresponding to the ratio of ^{the heat generation density [W / mm 2} ] of the heat blocks 331a to 331d on the central side and the heat blocks 332 on both ends.

Alternatively, the width, length or thickness of the resistance adjusting portion 338 is formed according to the ratio of ^{the electric resistance, the energization path length or the heat generation area (mm 2} ) of the central heat blocks 331a to 331d and the heat blocks 332 on both ends. do. By doing so, it is possible to adjust the magnitude of the resistance value of the heat blocks 331a to 331d and 332 on the center side and both end sides to make the heat generation density uniform.

Instead of reducing the resistance values of the central heat blocks 331a to 331d, it is conceivable to make the heat generation density uniform by narrowing the cross section of the resistance pattern of the heat blocks 332 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.

A plurality of methods are possible for forming the resistance adjusting portion 338. That is,
1) A method of forming a meandering resistance pattern by partially cutting out and embedding a resistance adjusting portion 338 in the missing portion of the pattern (the method of FIG. 3A described above).
2) A method of partially overwriting the resistance adjusting portion 338 on the meandering resistance pattern of the heat blocks 331a to 331d 3) After partially forming the resistance adjusting portion 338 on the base material in advance, the heat blocks 331a to A method of overwriting the meandering resistance pattern of 331d 4) A method of partially ion-implanting a predetermined dopant into the meandering resistance pattern is possible.

The heat blocks 331a to 331d and the heat blocks 332 are provided with contact thermistors TH1 to TH6 as temperature detecting members. That is, thermistors TH1 to TH4 are arranged in the central heat blocks 331a to 331d, respectively, and the thermistors TH5 and TH6 are arranged in the end side heat blocks 332, respectively. The contact thermistors TH1 to TH6 can be arranged, for example, on the back side of the heater base material 360.

Further, thermostats S1 and S2 are arranged in one heat block 331c on the center side and one heat block 332 on the end side. The thermostats S1 and S2 are current cutoff members (safety elements) that prevent the heater member 330 from abnormally generating heat due to a failure of the thermistors TH1 to TH6, a short circuit of the triac of the control device, a failure of the CPU, etc. be. The thermostats S1 and S2 can be arranged, for example, on the back side of the heater base material 360.

It is usually desirable that the thermistors TH1 to TH6 are arranged at the center of the heat generating region of each heat block. However, in the present embodiment, the resistance adjusting portion 338 is formed at a position close to the center of the heat block.

Since the resistance adjusting unit 338 has a low resistance and a low heat generation density, if the temperature detecting member is arranged close to the resistance adjusting unit 338, a temperature lower than the temperature that should be originally detected is detected. If the temperature is controlled at a low detected temperature, the temperature of the heat block becomes higher than the target temperature, and there is a risk of abnormal images such as hot offset and gloss abnormality.

Therefore, thermistors TH1 to TH4 are arranged apart from the resistance adjusting unit 338. In FIG. 3A, since the resistance adjusting portion 338 is formed in a meandering pattern of the second stage from the upstream side, the thermistors TH1 to TH4 are arranged at the center of the first stage on the upstream side in the longitudinal direction. As a result, it is possible to prevent the influence of the resistance adjusting unit 338 from affecting the thermistors TH1 to TH4.

On the contrary, as shown in FIG. 3B, thermistors TH1 to TH4 can be arranged on the downstream side of the resistance adjusting unit 338. In FIG. 3B, thermistors TH1 to TH4 are arranged at the center of the meandering pattern on the most downstream side, that is, the fourth stage from the upstream side in the longitudinal direction. Since there is an interval of two stages of the meandering pattern between the resistance adjusting unit 338 and the thermistors TH1 to TH4, the influence of the resistance adjusting unit 338 is less likely to affect the thermistors TH1 to TH4.

The thermistors TH5 and TH6 of the heat blocks 332 on both ends are arranged on the extension line in the longitudinal direction of the arrangement positions of the thermistors TH1 to TH4. As a result, the temperature information from the thermistors TH1 to TH6 can be obtained in the short direction under the same positional conditions, so that the occurrence of temperature unevenness of the fixing belt can be suppressed by controlling the control device based on the temperature information.

When the thermistor TH4 is arranged on the resistance adjusting unit 338 as shown in FIG. 4, a temperature lower than the temperature that should be originally detected is detected, and the temperature control is performed at this lower detected temperature. Then, the temperature of the heat block becomes higher than the target temperature, and there is a risk of abnormal images such as hot offset and gloss abnormality.

The arrangement of the resistance adjusting unit 338 and the thermistors TH1 to TH4 is not limited to FIGS. 3A and 3B described above. For example, as shown in FIGS. 5A to 5F, the resistance adjusting unit 338 and the thermistor TH can be arranged.

5 (a) to 5 (f) show the heat blocks 331d representing the central heat blocks 331a to 331d and the heat blocks 332 on both ends. In FIG. 5A, the resistance adjusting portion 338 is formed on the most downstream side in the paper transport direction, and the thermistor TH4 is arranged in the center of the second stage from the upstream side. By wiring the resistance adjusting unit 338 closer to the most downstream side in the paper transport direction, the heat generation density around the thermistors TH1 to TH4 becomes high, and the temperature of the heater member 330 can be controlled at an appropriate temperature.

Also in the case of FIG. 5, the thermistors TH6 (TH5) of the heat blocks 332 on both ends are arranged on the extension line in the longitudinal direction of the arrangement positions of the thermistors TH1 to TH4. As a result, the temperature information from the thermistors TH1 to TH6 can be obtained in the short direction under the same positional conditions, so that the occurrence of temperature unevenness of the fixing belt can be suppressed by controlling the control device based on the temperature information.

In FIG. 5B, the resistance adjusting portion 338 is formed on the most upstream side in the paper transport direction, and the thermistor TH4 is arranged in the second stage from the downstream side. Since there is a distance between the resistance adjusting unit 338 and the thermistor TH4, the heat generation density is high around the thermistor TH4, and the temperature of the heater member 330 can be controlled at an appropriate temperature.

In FIG. 5C, the resistance adjusting portion 338 is divided into three parts and formed in a dispersed manner. That is, the first resistance adjusting portion 338a and the second resistance adjusting portion 338b are formed at both ends of the second stage from the downstream side, and the third resistance adjusting portion 338c does not overlap with these resistance adjusting portions 338a and 338b in the lateral direction. As shown above, it is formed in the center on the most downstream side.

The thermistor TH4 is arranged in the center of the second stage from the upstream side. By forming the three resistance adjusting portions 338a to 338c in a dispersed manner in this way, the heat generation density in the heat generation region of the heat block 331d can be made uniform.

In FIG. 5D, the resistance adjusting portion 338 is divided into three parts and formed in a dispersed manner, and the first resistance adjusting portion 338a and the second resistance adjusting portion 338b are formed at both ends on the most downstream side in the paper transport direction to adjust the third resistance. The portion 338c is formed in the center on the most upstream side. The thermistor TH4 is arranged in the center of the third stage from the upstream side in the longitudinal direction.

In FIG. 5 (e), the resistance adjusting portion 338 is divided into five and formed in a dispersed manner. That is, the first resistance adjusting portion 338a is formed at the left end of the uppermost stream, and the second resistance adjusting portion 338b and the third resistance adjusting portion 338c are formed so as to sandwich the thermistor TH4 from the left and right in the second stage from the upstream side. The fourth resistance adjusting portion 338d is formed at the right end of the third stage from the upstream side, and the fifth resistance adjusting portion 338e is formed at the center in the longitudinal direction on the most downstream side.

In FIG. 5 (f), the resistance adjusting portion 338 is similarly divided into five and formed in a dispersed manner, the first resistance adjusting portion 338a is centered in the longitudinal direction of the uppermost stream, and the second resistance adjusting portion 338b is located at the right end of the second stage from the upstream side. To form. The third resistance adjusting unit 338c and the fourth resistance adjusting unit 338d are formed so as to sandwich the thermistor TH4 from the left and right at the third stage from the upstream side, and the fifth resistance adjusting unit 338e is formed at the left end on the most downstream side. ..

(Single type heater)
The embodiment described above is a dual type heater member, but FIG. 6 shows an example of a single type heater member 330. The heater member 330 has two electrode portions 339a and 339b, and a current is supplied from the power supply PW by a feeder line 351 to 353 connected to the electrode portions 339a and 339b.

A switch SW is arranged between the feeder lines 351 and 352, and the current from the power supply PW to all the heat blocks is collectively supplied / cut off by turning the switch SW ON / OFF. Similar to FIG. 3B, the single type heater member 330 is also provided with a resistance adjusting unit 338, thermistors TH1 to TH6, and thermostats S1 and S2.

Even in the single type heater member 330, when the thermistor TH is arranged so as to overlap the resistance adjusting unit 338 as shown in FIG. 6B, a temperature lower than the temperature that should be originally detected is detected, and hot offset, gloss abnormality, etc. There is a risk of abnormal image generation. Therefore, as shown in FIG. 6A, the thermistors TH1 to TH4 are arranged apart from the resistance adjusting unit 338.

The arrangement of the resistance adjusting portion 338 and the thermistors TH1 to TH4 of the single type heater member 330 is not limited to FIG. 6A described above. For example, as shown in FIGS. 7A to 7F, the resistance adjusting unit 338 and the thermistor TH can be arranged.

7 (a) to 7 (f) show heat blocks 331a representing the central heat blocks 331a to 331d. In FIG. 7A, the resistance adjusting portion 338 is formed on the most downstream side in the paper transport direction, and the thermistor TH1 is arranged at the right end of the second stage from the upstream side. In FIG. 7B, the resistance adjusting portion 338 is formed on the most upstream side in the paper transport direction, and the thermistor TH1 is arranged at the right end of the second stage from the downstream side.

In FIG. 7C, the resistance adjusting portion 338 is divided into two and formed in a dispersed manner. That is, the first resistance adjusting portion 338a is formed on the left side from the center in the longitudinal direction of the second stage from the downstream side, and the second resistance adjusting portion 338b is formed on the right side from the center in the longitudinal direction on the most downstream side.

The thermistor TH1 is arranged at the right end of the second stage from the upstream side. By forming the three resistance adjusting portions 338a and 338b in two in this way, the heat generation density in the heat generation region of the heat block 331a can be made uniform.

Also in FIG. 7D, the resistance adjusting portion 338 is divided into two and formed in a dispersed manner, the first resistance adjusting portion 338a is formed at the right end of the uppermost stream, and the second resistance adjusting portion 338b is formed at the leftmost downstream side. There is. The thermistor TH1 is arranged at the right end of the third stage from the upstream side.

In FIG. 7 (e), the resistance adjusting portion 338 is divided into four parts and formed in a dispersed manner. That is, the first resistance adjusting unit 338a is on the left end of the uppermost stream, the second resistance adjusting unit 338b is on the left side of the second stage from the upstream side toward the center, and the third resistance adjusting unit 338c is on the left side of the third stage from the upstream side. On the right side, the fourth resistance adjusting portion 338d is formed at the right end on the most downstream side. The thermistor TH1 is arranged at the right end of the second stage from the upstream side.

In FIG. 7 (f), the resistance adjusting portion 338 is similarly divided into four and formed in a dispersed manner, the first resistance adjusting portion 338a is located at the right end of the uppermost stream, and the second resistance adjusting portion 338b is located near the center of the second stage from the upstream side. The third resistance adjusting portion 338c is formed on the right side, the third resistance adjusting portion 338c is formed on the left side near the center of the third stage from the upstream side, and the fourth resistance adjusting portion 338d is formed on the left end on the most downstream side. The thermistor TH1 is arranged at the right end of the third stage from the upstream side.

FIG. 8 shows heat blocks 331a to 331d and 332 in which adjacent ends thereof are overlapped with each other at the same inclination in the lateral direction. As a result, the gaps between the heat blocks 331a to 331d and 332 in the lateral direction are eliminated, and the temperature unevenness in the fixing belt 310 is eliminated. Others are the same as in FIG. 3A.

(Modification example of fixing device)
The present invention is applicable to the fixing device as shown in FIGS. 9 to 11 in addition to the fixing device described above. Hereinafter, the configurations of the fixing devices shown in FIGS. 9 to 11 will be briefly described.

First, in the fixing device 300 shown in FIG. 9, 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 heater 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. 10, the above-mentioned pressing roller 370 is omitted, and the heater member 330 is the fixing belt 310 in order to secure the circumferential contact length between the fixing belt 310 and the heater member 330. 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.

Finally, in the fixing device 300 shown in FIG. 11, 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. 2B.

(Other Features of the Present Invention)
Although the present invention has been described above, the features of the present invention can be described in the claims as well as the following features 1 to 6.
[Feature 1]
A heater member in which resistance adjusting portions are formed at the same positions in the lateral direction of the heater base material with respect to a plurality of heat blocks in which temperature detecting members are arranged.
[Feature 2]
A heater member in which a resistance adjusting portion is formed at a position where the heat generation density is the same for a plurality of heat blocks in which a temperature detection member is arranged.
[Feature 3]
A heater member in which a resistance adjusting portion is formed on the upstream side of the temperature detecting member in the paper transport direction in a plurality of heat blocks in which the temperature detecting member is arranged.
[Feature 4]
A heater member in which a resistance adjusting portion is formed on the downstream side of the temperature detecting member in the paper transport direction in a plurality of heat blocks in which the temperature detecting member is arranged.
[Feature 5]
A heater member in which resistance adjusting portions are formed on the upstream side and the downstream side of the temperature detecting member in the paper transport direction in a plurality of heat blocks in which the temperature detecting member is arranged.
[Feature 6]
A heater member in which resistance adjusting portions are formed at equal intervals in the lateral direction of the heater base material in a plurality of heat blocks in which temperature detecting members are arranged.

Although the configurations of various fixing devices have been described above, the temperature detection member used in the heater member according to the present invention is not limited to the contact type thermistor, and other temperature sensors may be used. Further, the heater member can be applied not only to a type fixing device that directly heats a thin-walled fixing belt, but also to a heat roller type fixing device in which a heater member is arranged on the inner circumference. Further, the heater member according to the present invention is not applied only to the fixing device. For example, the heater member according to the present invention can be applied to a drying device mounted on an inkjet image forming device and a heater of an inkjet print head in order to dry the ink applied to the paper.

Further, in the above embodiment, the longitudinal length L1 of the central heat block is set longer than the longitudinal length L2 of the heat blocks at both ends (L2 <L1), but the number and length of the heat blocks are changed. Therefore, it is possible to reverse this magnitude relationship (L2> L1), and in that case, a resistance adjusting portion is formed toward the heat blocks at both ends. Then, the temperature detection member is arranged so as not to overlap with the resistance adjusting portions of the heat blocks at both ends.

Further, the heater 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 heater 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 resistance pattern of the heater member can be formed in any shape such as a comb tooth shape or a spiral shape in addition to the meandering shape.

1Y, 1M, 1C, 1Bk: Image drawing unit 2: Photoreceptor (image carrier)
3: Charging device 4: Developing device 4: Central side 4a: Developer carrier 5: Cleaning device 5: Drum cleaning device 5a: Cleaning blade 6: Exposure device 6a: Mirror 7: Paper feeding device 7a: Mirror 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 feeding device 60: Paper feed roller 100: Image forming device 103: Image forming Device body 250: Resist roller pair 300: Fixing device 310: Fixing belt 320: Pressurized roller 321: Iron core metal 321: Core metal 322: Elastic layer 323: Demolding layer 330: Heater member 330a: Base material layer 330b: First 1 Insulation layer 330c: Heat generating portion 330d: Conductor layer 330e: Second insulation layer 330f: Third insulation layer 331a to 331d: Central side heat block 332: Both ends side heat block 333 to 335: Electrode portion
336, 339, 340, 341: Conductive wire 337b: Heat block on both ends 338: Resistance adjustment part 338a to 338e: Resistance adjustment part 339a, 339b: Electrode part 350: Stay 351-355: Feed line 360: Heater base material 370: Pressing roller 380: Nip forming member 381: Stay 390: Pressurizing belt Lb: Laser beam N: Transfer nip N: Nip part N1: Heating nip (first nip part)
N2: Fixing nip (second nip part) P: Paper PW: Power supply S1, S2: Thermostat SW, SW1, SW2: Switch TH1 to TH6: Thermistor TM: Transfer means

Japanese Patent No. 45122232

Claims (8)

A heat block having a resistor that generates heat when energized and formed on the surface of the base material,
A resistance adjusting unit having an electric resistance smaller than the electric resistance of the resistor and formed in the energization path of the heat block.
It has a temperature detecting member arranged so as to be able to detect the temperature of the heat block.
A heater member characterized in that the temperature detecting member is arranged at a position separated from the resistance adjusting portion. The heater member according to claim 1, wherein the resistance adjusting portion and the temperature detecting member are arranged at different positions in the longitudinal direction of the base material. The heater member according to claim 1 or 2, wherein the resistance adjusting portion and the temperature detecting member are arranged at different positions in the lateral direction of the base material. The heater member according to any one of claims 1 to 3, wherein the heat generation densities of the plurality of heat blocks are made uniform by the resistance adjusting unit. 3. Heater member. A heating device, characterized in that the member to be heated is heated by the heater member according to any one of claims 1 to 5. A flexible sleeve-shaped rotating member and
The heater member according to any one of claims 1 to 5, wherein the heating region is in sliding contact with the inner circumference of the rotating member.
It has a pressurizing member that sandwiches the rotating member and press-contacts the heater member to form a nip portion between the rotating member.
A fixing device characterized in that heat of the heater 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 7.

Images