JP2006019159A - Heater and image heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize high throughput for each kind of paper by suppressing the temperature rise of a paper non-passing part by changing the resistance value of a heater, and to satisfy fixing property in a paper passing region and prevention of defective images. <P>SOLUTION: This heater has a substrate the longitudinal direction of which is perpendicular to the paper passing direction of a material to be heated, and resistance heating elements 31, 32 on the substrate, and heats a material to be heated. This heater is structured so as to include a region in which the resistance value of the resistance heating element becomes gradually small from a reference position to a longitudinal end part, and another region in which the rate of change of the resistance value is not uniform in the middle of the above region. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention has a substrate, a resistance heating element provided along the longitudinal direction of the substrate, and a heating element used in a heating device for heating a material to be heated, and the heating element. For example, the present invention relates to a heating device suitable as a fixing device mounted on an image forming apparatus.

  Conventionally, in an image forming apparatus such as an electrophotographic copying machine or a laser beam printer, an unfixed toner image formed and supported on a recording material by a transfer method or a direct method in an image forming process means section As a fixing device for fixing as a permanently fixed image, a toner image is heated by sandwiching and conveying a recording material as a heated material by a fixing roller heated to a predetermined temperature and a pressure roller pressed against the fixing roller. A heat roller type heating device for pressure fixing is generally used.

  Recently, in order to achieve power saving and shortening the time from power-on to image output, as described in Patent Document 1, at least a fixedly supported heating body (hereinafter referred to as a heater), And a heater unit comprising a heat-resistant film (hereinafter referred to as a fixing film) as a flexible member that is conveyed while being pressed against the heater, and a pressure member (hereinafter referred to as a pressure-sensitive member) that adheres a recording material to the heater unit. A fixing device (film heating method) configured to heat and fix the toner image formed on the surface of the recording material by applying the heat of the heater to the recording material through the fixing film. Has been proposed.

  Conventionally, such a fixing device uses a heater as shown in FIG. This heater is basically composed of a substrate 100 and resistance heating elements 101 and 102 provided along the longitudinal direction of the substrate, and is electrically connected to both ends of the resistance heating elements 101 and 102. The resistance heating elements 101 and 102 generate heat by supplying power to the resistance heating elements 101 and 102 from the feeding electrodes a, b and c. As shown in the lower graph, the resistance heating elements 101 and 102 of the heater have resistance values that are uniform in the longitudinal direction.

  In this way, the film heating type fixing device having the heater in which the resistance heating elements 101 and 102 uniformly generate heat in the longitudinal direction is in contact with the recording material through the fixing film having a low heat capacity, and transfers heat. On-demand fixing is possible, but when a recording material having a relatively short width with respect to the longitudinal width of the resistance heating elements 101 and 102 is continuously conveyed, the sheet is fed through a pressure roller where the heater is in close contact with the fixing film. The difference in surface temperature between the paper part and the non-sheet-passing part becomes large, and the outer diameter and the friction coefficient may change with the length of the pressure roller.

Therefore, Patent Document 2 discloses a heater that can cope with various long letter sizes and suppresses the temperature rise of the non-sheet passing portion. As shown in FIG. 11, this heater has resistance heating elements 103 and 104 that continuously suppress the heat generation at the end portion, so that the temperature rise at the non-sheet passing portion can be suppressed. As shown in the lower graph, the resistance heating elements (main heater and sub-heater) 103 and 104 of this heater continuously change in resistance value per longitudinal unit length as shown in the lower graph. Such a heater having the resistance heating elements 103 and 104 generates heat at the end portion from the central portion by increasing the difference between the resistance value at the central portion and the resistance value at the end portion of the resistance heating elements 103 and 104 as shown in FIG. Can be achieved and high throughput can be realized.
JP-A-63-313182 Japanese Patent Laid-Open No. 10-177319

  The present invention is a further development of the technique of Patent Document 2 described above.

  An object of the present invention is to add a new circuit or member to this type of heater and a heating device using the heater, and to change the resistance value change amount of the resistance heating element in the longitudinal direction, so that the non-sheet passing portion To suppress the temperature rise and to maintain the temperature difference within a certain temperature within the paper passing area to prevent hot offset, unfixed image, and cold offset.

  A typical configuration of a heating body according to the present invention for achieving the above object includes a substrate and a resistance heating element provided along the longitudinal direction of the substrate, and heats a material to be heated. In the heating element used in the heating device, the substrate is provided with a plurality of resistance heating elements in the short direction of the substrate, and at least one resistance heating element has a resistance value per unit length in the longitudinal direction. In areas other than those corresponding to the safety element installation part and temperature detection element installation part for the substrate, the resistance value change amount per unit length of the area where the resistance value changes becomes non-uniform. It is a heating element characterized by being.

  In addition, a typical configuration of the heating device according to the present invention for achieving the above object includes a heating body fixedly supported by a support, a safety element and a temperature detection element installed on a substrate of the heating body, A flexible member that moves while being in contact with the heating body, and a pressure member that forms a nip with the heating body across the flexible member, and the material to be heated is sandwiched between the nip portions. In the heating apparatus that heats while transporting, the heating body is formed on the substrate along the longitudinal direction of the substrate, and arranged in the transported material transport direction, with the substrate extending in the direction intersecting the heated material transport direction A plurality of resistance heating elements, and at least one resistance heating element among the plurality of resistance heating elements per unit length between the conveyance reference of the material to be heated and the longitudinal end portion. Safety element installation part with respect to the board, which has a region where the resistance value changes In a region other than that corresponding to the temperature sensing element mounting portion, the heating device having a resistance value variation amount per unit length of the region where the resistance value is changed, characterized in that it has a non-uniform, it is.

  The position where the amount of change in resistance value of the heating body becomes non-uniform may be a position that matches the desired paper type as the material to be heated.

  Further, in the image forming apparatus in which the minimum length paper size of the recording material to be heated is defined, the position where the amount of change in the resistance value of the heating body is not uniform may be a position that matches the minimum length paper size. .

  According to the present invention, for example, as a fixing device, a new member is not added, the amount of heat generated at the end is suppressed, the temperature rise at the non-sheet passing portion at the time of continuous feeding of each paper type size is suppressed, and a small size is desired as well as a desired size It is possible to achieve both increased paper size throughput and temperature control to keep the temperature difference within the paper passing area below a certain temperature and prevent hot offset, unfixed images, and cold offset. It has the effect of becoming.

  Hereinafter, a first embodiment of the present invention will be described.

(1) Example of Image Forming Apparatus FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus according to the present embodiment. Reference numeral 1 denotes a scanner unit, which has optical means and scanning means for irradiating and scanning a laser beam 1a transmitted according to image information. Reference numeral 10 denotes a process cartridge incorporating main image forming means. A photosensitive drum (electrophotographic photosensitive member) 3 as a latent image holding member, a roller charger 4 made of semiconductive rubber, and a toner 6 are placed on the photosensitive drum 3. And a cleaner 8 for removing waste toner from the photosensitive drum 3. The photosensitive drum 3 in the process cartridge 10 rotates in the clockwise direction indicated by the arrow, and the surface thereof is uniformly charged by the roller charger 4. By irradiating the uniformly charged surface of the photosensitive drum 3 with the laser beam 1 a transmitted from the scanner unit 1 through the mirror 2, an electrostatic latent image is formed on the surface of the photosensitive drum 3. It has become. The electrostatic latent image is supplied with toner by the developing device 5 and is visualized as a toner image.

  On the other hand, a transfer material (weighing 64 to 128 g) as a recording material in the paper feed cassette 11 is separated and fed one by one by a paper feed roller 13 and a separation roller pair 13a. The fed transfer material 12 is reversed by the U-turn sheet path 13 b and conveyed to the pair of registration rollers 15 along the upper and lower guides 14. The registration roller 15 stops rotating until the transfer material 12 arrives, and the skew of the transfer material 12 is corrected by receiving the front end of the transfer material 12 against the nip portion.

  Next, the registration roller 15 conveys the transfer material 12 to a transfer portion which is a contact nip portion between the photosensitive drum 3 and the transfer roller 7 so as to synchronize with the leading edge of the image formed on the photosensitive drum 3. In addition, a paper feed sensor (not shown) is installed near the registration roller 15 to detect a paper passing state, a jam, and a length of a transfer material.

  The transfer material 12 conveyed to the transfer portion as described above is given a charge opposite in polarity to the toner from the transfer roller 7 from the back side, and the toner image formed on the photosensitive drum 3 is transferred to the transfer material 12. The

  The transfer material 12 onto which the toner image has been transferred is conveyed to a fixing device 18 by a conveyance guide 16 and a conveyance roller 17. The fixing device 18 forms a recorded image by dissolving and fixing the unfixed toner image on the transfer material 12 on the transfer material 12 with heat and pressure.

  The transfer material 12 after image fixing is guided to the U-turn sheet path 19a side by the flapper 19 and discharged onto the first discharge tray 20 when discharge in the image surface downward mode is designated. When discharge in the image surface upward mode is specified, the flapper 19 guides the straight sheet path 19b to the second discharge tray 21 and discharges it.

  Here, in the image forming apparatus of the present embodiment, the conveyance reference of the transfer material 12 as the recording material is the central reference of the paper center in all conveyance paths.

(2) Fixing device 18
Next, the fixing device 18 will be described in detail with reference to FIG. The fixing device 18 of this embodiment is a heating device of a film heating type of a pressure roller drive type and a tensionless type.

a) Overall Schematic Configuration 22 of the Apparatus 18 A heat-resistant stay holder 22 as a heating body support, which is a heat-resistant member having a substantially semicircular saddle shape in cross section. A heating body (hereinafter referred to as a heater) 23 is fitted into a groove provided along the length of the holder on the lower surface of the stay holder 22 and fixedly supported. The structure of the heater 23 will be described in detail in the next item b).

  Reference numeral 24 denotes a cylindrical thin film (hereinafter, referred to as a fixing film) such as polyimide having excellent heat resistance as a flexible member, which is loose with respect to the stay holder 22 on which the heater 23 is fixedly supported. It is fitted outside.

  At least the above-mentioned stay holder 22, heater 23, and fixing film 24 constitute a heater unit.

  Then, a heater 23 on the lower surface of the stay holder 22 and an elastic pressure roller 25 as a pressure member are sandwiched by a fixing film 24 to resist the elasticity of the pressure roller 25 by a pressure means (not shown). A fixing nip portion N having a predetermined width necessary for heat fixing is formed by pressing with a predetermined pressing force.

The pressure roller 25 has an elastic layer 27 made of silicon rubber or the like formed on the outer side of the core metal 26, and a tube made of PFA, PTFE or the like having excellent release properties as a release layer 28 on the outer side thereof. The heat conductivity of the pressure roller 25 is 0.5 × 10 ³ W / ° C. · cm.

  The pressure roller 25 is rotationally driven by the driving means M in the counterclockwise direction indicated by the arrow (pressure roller drive type). Then, the rotational force acts on the cylindrical fixing film 24 by the contact frictional force in the fixing nip N between the roller 25 and the outer surface of the fixing film 24 by the rotational driving of the pressure roller 25, and the fixing film 24 becomes a stay holder. The outer surface of the film 22 rotates in the clockwise direction of the arrow while the inner surface of the film is in close contact with the downward surface of the heater 23 in the fixing nip portion N and slides.

  In the state where the fixing film 24 is rotated by the rotation driving of the pressure roller 25 and the heater 23 is heated to a predetermined target temperature by energizing the heater 23 as will be described later, the fixing nip N A transfer material (recording material) 12 as a heated material carrying an unfixed toner image ta is introduced between the fixing film 24 and the pressure roller 25, and the toner image carrying surface is in close contact with the outer surface of the fixing film 24. By passing through the fixing nip N together with the fixing film 24, the heat of the heater 23 is applied to the transfer material 12 through the fixing film 24, and the unfixed toner image ta is heated and fixed on the surface of the transfer material 12 by tb. The The transfer material 12 that has passed through the fixing nip N is separated from the surface of the fixing film 24 and is discharged and conveyed.

  The stay holder 22 functions as a support member for the heater 23, and also serves to pressurize the fixing nip N and to rotate and stabilize the cylindrical fixing film 24.

  The inner surface of the fixing film 24 rotates while sliding on the lower surface of the heater 23 in the fixing nip portion N and on the outer surface of the stay holder 22 in the vicinity of the fixing nip portion N. In order to rotate the fixing film 24 smoothly with low torque, the frictional resistance between the heater 23 and the stay holder 22 and the fixing film 24 is kept small. For this reason, a small amount of lubricant such as heat-resistant grease is interposed between the heater 23 and the stay holder 22 and the fixing film 24. As a result, the fixing film 24 can smoothly rotate.

  The fixing film 24 is a member having a small heat capacity, and has a thickness of 100 μm or less and has heat resistance and thermoplasticity such as polyimide, polyamideimide, PEEK, PES, PPS, PFA, PTFE, FEP, etc. It is. Further, the film needs to have a thickness of 20 μm or more as a film having sufficient strength and excellent durability for constituting a long-life fixing device. Therefore, the thickness of the fixing film 24 is optimally 20 μm or more and 100 μm or less. Further, in order to prevent offset and ensure the separation of the recording material, the surface layer of the fixing film is mixed or singly coated with a heat-resistant resin having good releasability such as PFA, PTFE, FEP, and silicone resin.

  Various image forming apparatuses such as printers and copiers that use such a film heating type fixing device eliminate the need for preheating during standby and shorten the wait time due to high heating efficiency and rapid start-up. There are many advantages over the conventional method of heat fixing using a heat roller or the like.

b) Heater 23
3A is a plan model diagram of the heater surface side, FIG. 3B is a plan model diagram of the heater surface side with the surface protective layer removed, and FIG. 3C is a plan model diagram of the heater back side. FIG. 4 is an enlarged cross-sectional model view taken along line (4)-(4) in FIG. 3 (3).

  Reference numeral 30 denotes a heater substrate. The heater substrate 30 is a heat-resistant, heat-conductive, and electrically insulating ceramic material such as alumina or aluminum nitride, and is a horizontally long thin plate member whose longitudinal direction is a direction intersecting (orthogonal) with the recording material conveyance direction D. .

  Reference numerals 31 and 32 denote first and second resistance heating elements (hereinafter referred to as a main heater and a sub-heater) which are formed and formed on the surface side of the heater substrate 30 as a heating element that generates heat by energization by thick film printing. is there.

  The main heater 31 and the sub heater 32 are respectively formed along the heater substrate longitudinal direction and arranged in the recording material conveyance direction (heater substrate short direction). The main heater 31 and the sub-heater 32 have different heat generation distributions in the longitudinal direction, and the main heater 31 has a longitudinal length with respect to the resistance heating element portion other than the resistance heating element portion corresponding to the safety element or temperature detection element installation position described later. The sub-heater 32 has a heat generation distribution resistor pattern in which the heat generation amount increases from the center to the end in the longitudinal direction. . The combined heat generation amount of the heat generation amount of the main heater 31 and the heat generation amount of the sub-heater 32 is substantially constant in the longitudinal direction of the resistance heat generation member except for the resistance heat generation portion corresponding to the safety element and the temperature detection element installation position. Regarding the sub-heater 32, the amount of heat generated at the portion corresponding to the installation position of the safety element or the temperature detection element is not the maximum in the longitudinal direction of the resistance heating element. Further, in this embodiment, only the heat generation amount of the portions 32a and 32b corresponding to the safety element and temperature detection element installation position of the sub-heater 32 is increased with respect to the heat generation amount of the portion adjacent to the safety element and temperature detection element installation position.

  Reference numeral 33 denotes a feeding electrode portion (hereinafter referred to as a main contact) formed by electrical conduction to one end portion in the longitudinal direction of the main heater 31, and 34 is electrically conducted to one longitudinal end portion of the sub-heater 32. The formed power supply electrode portion (hereinafter referred to as a sub-contact), 35 is a power supply electrode portion (hereinafter referred to as “common contact”) formed by electrically connecting to the other longitudinal end portions of the main heater 31 and the sub-heater 32. Is referred to as a common contact).

  The main contact 33, the sub contact 34, and the common contact 35 are all formed as conductor patterns by thick film printing on the surfaces on both ends of the heater substrate.

  A surface protective layer 36 is formed on the surface of the heater substrate 30 so as to cover the main heater 31, the sub heater 32, a part of the main contact 33, a part of the sub contact 34, and a part of the common contact 35. . This surface protective layer 36 is formed as a glass coat pattern by thick film printing. The inner surface of the fixing film 24 is in close contact with the surface of the surface protective layer 36 and slides.

  Reference numeral 37 denotes a temperature detection element such as a thermistor. In this example, it is a thermistor, and is disposed in contact with a position corresponding to the sheet passing area width of the minimum size recording material on the back surface side of the heater substrate 30.

  Reference numerals 38 and 39 denote lead electric circuits (hereinafter referred to as thermistor contacts) electrically connected to the thermistor 37. The thermistor contacts 38 and 39 are formed on the back surface of the heater substrate as a conductor pattern by thick film printing.

  Reference numeral 40 denotes a safety element such as a thermo switch or a thermo fuse. In this embodiment, a thermo switch is used. The thermo switch 40 is disposed on the back side of the heater substrate 30 so as to be in contact with a position substantially corresponding to the central reference line E that is the recording material conveyance reference (= the central portion in the longitudinal direction of the heat generation area of the heater 23).

  In FIG. 3A, A is the maximum sheet passing area width. The lengths of the main heater 31 and the sub heater 32 in the longitudinal direction substantially correspond to the maximum sheet passing area width A. B is a sheet passing area width of the small size recording material. C and C are non-sheet passing area widths ((A−B) / 2) when a small size recording material is passed.

  In this embodiment, the maximum size recording material that can be used for passing paper is full bleed paper having a longitudinal width of 312 mm, and the maximum paper passing area width A corresponds to the longitudinal width of 312 mm.

FIG. 5 is a block circuit diagram of a power supply control system for the heater 23. Reference numeral 50 denotes a control unit (engine controller, CPU). 51 is an AC power source. 52 and 53 are first and second triacs. And
a: AC power source 51 → thermo switch 40 → first triac 52 → main contact 33 → main heater 31 → common contact 35 → AC power source 51
b: AC power source 51 → thermo switch 40 → second triac 53 → sub contact 34 → sub heater 32 → common contact 35 → AC power source 51
The two power supply paths (AC lines) of a and b are configured. Then, the control unit 50 controls the power supply to the main heater 31 and the sub heater 32 by controlling the first and second triacs 52 and 53.

  Further, the temperature information of the heater 32 detected by the thermistor 37 is fed back to the controller 50 as a digital signal through the thermistor contacts 38 and 39 (DC line).

  The controller 50 controls the first and second triacs 52 and 53 on the basis of the heater temperature detection information fed back from the thermistor 37 so that the heater temperature is maintained at a predetermined target temperature. The power supply to the sub heater 32 is controlled. Further, the first and second triacs 52 and 53 are controlled in accordance with the size information of the recording material 12 to be passed to control the power supply ratio to the main heater 31 and the sub heater 32.

  The thermo switch 40 as a safety element causes the heater 23 to overheat even if a situation (thermal runaway) occurs in which the heater 23 is continuously energized uncontrolled due to a failure of the control unit 50 or the like. It serves to shut off energization to the heater 23 by heat sensitivity (temperature detection).

  As described above, when the small-size paper is passed, the main heater 31 is mainly turned on to prevent the temperature rise of the non-paper passing portion, and the number of paper passing within a predetermined time can be increased. Can prevent paper wrinkles and gloss unevenness.

  In this embodiment, a thermo switch 40 is used as an electrical safety element of the heater 23. The thermo switch 40 is installed at a position that is the center of the resistance heating element and the center of the sheet passing. When a contact-type safety element is used, heater heating unevenness and a thermoswitch response time lag occur due to the heat capacity of the safety element. In order to prevent this problem, in this embodiment, the heat generation amount of the portion 32a corresponding to the portion of the sub heater 32 corresponding to the thermo switch is increased to compensate for the heat capacity of the thermo switch 40.

  The contact thermistor 37, which is a temperature detection element, also has a heat capacity that is not as high as that of the thermo switch 40. Therefore, in this embodiment, the heat generation amount of the portion 32b corresponding to the thermistor installation portion of the sub heater 32 is increased to increase the heat capacity of the thermistor 37. Compensate for minutes.

  The heater 23 will be described in more detail with reference to FIG. FIG. 6 is a resistance value distribution in the longitudinal direction of the main heater 31 and the sub heater 32 of the heater 23 in this embodiment. Both the main heater 31 and the sub heater 32 change the resistance value distribution from the center to both ends. The main heater 31 has a pattern shape that increases the amount of heat generated at the center, and the sub heater 32 has a pattern that increases the amount of heat generated at both ends. However, as described above, in the sub-heater 32, the portions corresponding to the safety element installation part and the temperature detection element installation part increase the heat generation amount to compensate for the heat capacity of the thermo switch 40 and the thermistor 37.

  In this embodiment, the rate of change of the resistance value is changed so that the sheet conveyance reference is ± 135 mm at the center reference (near the end of the LTR horizontal sheet: ± 135 mm in order to have a temperature gradient inside the LTR end). Using the heater 23 having the main heater 31 and the sub heater 32, the temperature difference in the letter size (LTR: about 261 mm × 279 mm) paper passing area is controlled within 20 ° C., and the LTR as well as the transfer material smaller than the LTR. In this example, it is possible to achieve both the increased throughput and the fixability of each paper type size.

  Here, with respect to the dimension positions in the longitudinal direction of the main heater 31 and the sub heater 32, the position of the longitudinal center (= center reference line E) is set to ± 0 mm position, and the longitudinal one end direction from this ± 0 mm position is set to a plus dimension position. The other end direction is a negative dimension position.

  Since the main heater 31 and the sub-heater 32, which are resistance heating elements of the heater 23, are manufactured by patterning by printing and printing on the substrate, it is possible to form a curved resistance heating element and realize an optimal heat distribution. it can. In order to realize the optimum heat generation distribution, a screen having a mesh size of 400 mesh or more is used from the usual 250 mesh (250 meshes in 254 mm × 254 mm) for the resistance heating element printing. As a result, resistance heating element patterns 31 and 32 that can change the resistance value of the main heater 31 and the sub-heater 32 continuously in the longitudinal direction and change the heat generation amount can be formed on the heater substrate 30.

  In this example, a heater having the following resistance heating element pattern was manufactured by the above manufacturing method, and a desired heat generation amount was realized.

  In the present embodiment, two resistance heating elements of the heater 23 are formed on the substrate 30 as the main heater 31 and the sub heater 32 as described above. As described above, the maximum size recording material that can be used in this embodiment is a full bleed sheet having a longitudinal width of 312 mm. In order to guarantee the printing area 305 mm of the full bleed sheet, the longitudinal widths of the main heater 31 and the sub heater 32 are used. Was 307 mm (± 153.5 mm from the center reference). The heater 23 is composed of a main heater 31 having a high resistance value per unit length at the center (hereinafter simply referred to as a resistance value) and a sub-heater 32 having a high resistance value at the end, which is a sheet passing reference.

  Further, in this embodiment, in order to suppress the heat generation amount of the non-sheet passing portion of the LTR, the main heater 31 and the sub heater 32 abruptly change the heat generation amount from the position of both ends ± 135 mm (near the LTR end portion) from the center reference E. ing. Specifically, with reference to FIG. 5, the change rate of the resistance value of the heater is changed as follows.

  For the main heater 31, the resistance value at the longitudinal center is 0.065Ω / mm, the resistance value at the position of ± 135mm near the LTR end is 0.0585Ω / mm, and the resistance value at the heater end ± 153.5mm is 0. 0.04875 Ω / mm.

  For the sub-heater 32, the resistance value of the portion adjacent to the installation position of the thermo switch 40 and the thermistor 37 at the longitudinal center is 0.65 Ω / mm, and the resistance value at the position of the LTR end ± 135 mm is 0.0715 Ω / mm, The resistance value of the heater end ± 153.5 mm was set to 0.08125Ω / mm.

c) Conventional heater [1]
The heater used in the conventional example (conventional example heater [1]) has resistance heating elements 101 and 102 having a constant resistance value in the longitudinal direction on the heater substrate 100 as shown in FIG.

d) Conventional heater [2]
The main heater 103 of the heater shown in FIG. 11 (conventional heater [2]) has a resistance value of 0.065 Ω / mm at the center and 0.0585 Ω / mm at the LTR end ± 135 mm. The resistance value of the heater end ± 153.5 mm is 0.052 Ω / mm.

  The sub heater 104 has a resistance value of 0.065 Ω / mm at the center, a resistance value at the position of the LTR end ± 135 mm is 0.0715 Ω / mm, and a resistance at the heater end is 0.078 Ω / mm.

e) Conventional heater [3]
FIG. 12 shows a heater (conventional example heater [3]) in which the difference between the resistance value at the center portion and the resistance value at the end portion is larger than that of the conventional example heater [2] in FIG.

  The resistance value at the center of the main heater 103 is 0.065 Ω / mm, the resistance value at the LTR end ± 135 mm is 0.052 Ω / mm, and the resistance at the heater end ± 153.5 mm is 0.0325 Ω / mm. It is.

  The resistance value at the center of the sub-heater 104 is 0.065 Ω / mm, the resistance value at the LTR end ± 135 mm is 0.078 Ω / mm, and the resistance at the heater end ± 153.5 mm is 0.0975 Ω / mm. is there.

  As described above, the fixing apparatus having the configuration including the heater of the embodiment of FIG. 6, the conventional heater [1] of FIG. 10, the conventional heater [2] of FIG. 11, and the conventional heater [3] of FIG. In the image forming apparatus equipped with the above, the throughput, fixability, and high temperature offset of the transfer material of each paper size were as follows (the throughput is the value when the temperature rise of the non-sheet passing portion of the heater is 300 ° C.) Show). The temperature control temperature of the heater for image fixing is 190 ° C. When continuous paper is passed, the temperature rise in the non-paper passing part is determined by the throughput. If the throughput is fast, the non-sheet passing portion temperature rises. In this embodiment, the throughput at which the temperature rise at the non-sheet passing portion is saturated at 300 ° C. is described during continuous paper feeding. Table 1 shows the results of A4 (210 mm × 297 mm) longitudinal paper having a small longitudinal width.

表１から、従来例ヒータ［１］のように抵抗値の変化が小さいと端部の発熱量が高くなり、非通紙部昇温が高くなるので、スループットは低下する。また、逆に従来例ヒータ［３］のように抵抗値の変化が大きいと端部の発熱量が低くなり、スループットアップが実現できる。実用性を考え、５枚/分以上をＯＫとする。

From Table 1, if the resistance value change is small as in the conventional heater [1], the heat generation amount at the end portion becomes high and the temperature rise at the non-sheet passing portion becomes high, so that the throughput decreases. In contrast, when the resistance value is greatly changed as in the conventional heater [3], the amount of heat generated at the end portion is reduced, and the throughput can be increased. Considering practicality, 5 sheets / minute or more is OK.

  Next, Table 2 shows the results of LTR landscape paper in which the main heater 31 is mainly lit.

  As shown in Table 2, when the change in resistance value is large as in the conventional heater [3], the fixing property at the end cannot be satisfied. If the temperature is adjusted at the end so as to satisfy the fixing property at the end, a hot offset occurs at the center. If the lighting of the sub-heater 32 is increased and the temperature difference in the LTR paper passing area is lowered, the throughput is lowered.

  Also, when each heater is A4 landscape paper, which is larger than A4 portrait, the sub-heater 32 is turned on in the same manner as the main heater 31 so that the non-sheet-passing portion is heated and fixed. Both are compatible.

  From the above results, by changing the rate of change of the resistance value at a certain longitudinal position like the heater of the present embodiment, it is possible to increase the throughput of LTR as well as the small size, fixability, and hot without adding other members. Both offsets can be achieved.

  In addition, in the heater having the resistance heating elements 31 and 32 having a stepped pattern in the longitudinal direction as shown in FIG. 7, the rate of change in the resistance value is increased so as to suppress the amount of heat generation at the end, thereby The same effect as the heater can be obtained.

  Further, the same effect can be obtained in the heater having the resistance heating elements 31 and 32 having the longitudinal pattern as shown in FIG.

  Hereinafter, a second embodiment of the present invention will be described. In the present embodiment, in the image forming apparatus in which the sheet passing conveyance standard of the transfer material 12 is the center reference and the sheet passing paper size is determined, the longitudinal width of the minimum sheet size from the sheet passing reference regarding the longitudinal resistance value of the resistance heating element. The resistance value up to the position of (± 35 mm) is constant, the resistance value decreases from the sheet passing reference to the longitudinal end, and the resistance change rate is A4 at the end position (± 148.5 mm) of the A4 landscape sheet. An example in which a fixing device having a heater that is lowered from within the lateral paper passing area can achieve both A4 throughput increase and fixability of each paper type size as well as a small size is shown.

  In the configuration of the image forming apparatus to which the present embodiment is applied, the description about the main body configuration, the fixing device configuration, and the heater manufacturing method that are the same as those in the first embodiment will be omitted. The image forming apparatus of this embodiment has a minimum longitudinal width of 70 mm (± 35 mm from the reference position) and a maximum longitudinal width of 312 mm (± 156 mm from the reference position).

  The heater 23 shown in this embodiment is shown in FIG. Three resistance heating elements 31, 32, 31 of the heater 23 of this embodiment are formed on the substrate 30. In order to guarantee a printing area of 310 mm, the longitudinal width of the resistance heating elements 31, 32, and 31 was 312 mm (± 156 mm from the center reference).

  A pair of resistance heating elements 31 and 31 (hereinafter, referred to as main heater 31) having a high central resistance value, which is a sheet passing standard (hereinafter, referred to as main heater 31), and a resistance heating element 32 having a high resistance value at the end portion ( Hereinafter, the heater 23 is constituted by a sub heater 32).

  Further, in this embodiment, since the minimum longitudinal width is ± 35 mm, it is not necessary to consider the temperature rise of the non-sheet passing portion up to ± 35 mm from the reference position. Therefore, a uniform resistance value is shown from the reference position to ± 35 mm. ing. Further, in order to suppress the amount of heat generated at the non-sheet passing portion of the A4 landscape paper, the resistance values of the main heater 31 and the sub heater 32 are abruptly changed from the positions of both ends ± 148.5 mm from the center reference. Specifically, the change rate of the resistance value of the heater is changed as follows.

  About the main heater 31, the resistance value of the central part from the reference position to ± 35 mm is 0.065 Ω / mm, the position from the reference position to ± 35 mm is 0.065 Ω / mm, and the position of the A4 lateral paper edge is ± 148.5 mm. The resistance value is 0.05525Ω / mm, and the resistance value of the heater end ± 156 mm is 0.039Ω / mm.

  As for the sub heater 34, the resistance value at the center is 0.065Ω / mm, 0.065Ω / mm from the reference position to ± 35mm, and the resistance value at the position of the A4 lateral paper edge ± 148.5mm is 0.07475Ω / mm. mm, the resistance value of the heater end ± 156 mm is 0.091 Ω / mm.

  Conventional heaters [1] to [3] (FIGS. 10 to 12) are the same as in the first embodiment.

  In the image forming apparatus equipped with the fixing device having the above-described heater, the throughput, fixing property, and high temperature offset of each paper size result are as follows (the throughput is the temperature rise of the non-sheet passing portion of the heater). Is displayed when the temperature reaches 300 ° C.).

  Table 3 shows the results of A4 longitudinal paper having a small longitudinal width.

表３から従来例ヒータ［１］のように、抵抗値の変化が小さいと端部の発熱量が高くなり、非通紙部昇温が高くなるので、スループットは低下する。また、逆に従来例ヒータ［３］のように抵抗値の変化が大きいと端部の発熱量が低くなり、スループットアップが実現できる。

From Table 3, as shown in the conventional heater [1], if the change in resistance value is small, the amount of heat generated at the end portion increases and the temperature rise at the non-sheet passing portion increases, so the throughput decreases. In contrast, when the resistance value is greatly changed as in the conventional heater [3], the amount of heat generated at the end portion is reduced, and the throughput can be increased.

  Next, Table 4 shows the result of A4 landscape paper in which the main heater 31 is mainly lit.

表４から、従来例ヒータ［３］のように抵抗値の変化量が大きいと端部の定着性が満足できない。端部の定着性を満足させると、中央部にホットオフセットが発生する。サブヒータの点灯を増加させ、Ａ４縦通紙領域内の温度差を低下させるとスループットが低下する。実用性を考え、５枚/分以上をＯＫとする。

From Table 4, if the amount of change in the resistance value is large as in the conventional heater [3], the fixing property at the end cannot be satisfied. When the fixing property at the end portion is satisfied, hot offset occurs at the center portion. If the lighting of the sub-heater is increased and the temperature difference in the A4 vertical paper passing area is lowered, the throughput is lowered. Considering practicality, 5 sheets / minute or more is OK.

  In addition, when each heater passes a transfer material that is larger than the longitudinal width A4 landscape paper, each heater is turned on in the same manner as the main heater 31 to turn on the sub-heater 32 and fix the non-sheet passing portion. Both sexes are compatible.

  As described above, in the present embodiment, when the paper passing size is defined, the resistance change rate is changed at a certain longitudinal position in accordance with the paper width width, so that it is small without adding other members. In addition to size, it is possible to achieve both LTR throughput increase, fixability, and hot offset.

  Hereinafter, a third embodiment of the present invention will be described. In the present embodiment, in the image forming apparatus in which the sheet conveyance reference of the transfer material 12 is the edge reference, the resistance value of the resistance heating element in the longitudinal direction decreases from the sheet feeding reference to the longitudinal edge, and letter (LTR). In a fixing device having a heater in which the rate of change in resistance value is lower than that in the LTR lateral paper region at the edge position (270 mm) of the horizontal paper, the throughput of the LTR as well as the small size is increased, and the fixability of each paper type size is The example which made it possible to achieve both is shown.

  In the configuration of the image forming apparatus to which the present embodiment is applied, the description of the main body configuration, the fixing device configuration, and the heater manufacturing method that are the same as those in the first embodiment will be omitted.

A heater 23 shown in this embodiment is shown in FIG. The heater of the present embodiment is an application of the heater paper passing standard used in the first embodiment to the end standard. Also, the conventional heaters [4], [5], and [6] used in this embodiment shown in FIG. 13 correspond to the conventional heaters [1], [2], and [3] used in Embodiment 1, respectively. However, the paper passing standard is applied to the edge standard. The ratio of the resistance value at the end to the central resistance value is the same as that in the first embodiment.
With respect to such a heater, as in Example 1, the throughput (sheet / min), fixability, and hot offset during A4 longitudinal paper feeding and LTR lateral paper feeding were measured for each heater. The results are shown below. Table 5 below shows the results when A4 paper is passed vertically.

表５から従来例ヒータ［４］のように、抵抗値の変化が小さいと端部の発熱量が高くなり、非通紙部昇温が高くなるので、スループットは低下する。また、逆に従来例ヒータ［５］のように抵抗値の変化が大きいと端部の発熱量が低くなり、スループットアップが実現できる。

From Table 5, as shown in the conventional heater [4], when the change in resistance value is small, the amount of heat generated at the end portion increases and the temperature rise at the non-sheet passing portion increases, so that the throughput decreases. On the contrary, if the resistance value is greatly changed as in the conventional heater [5], the amount of heat generated at the end becomes low, and the throughput can be increased.

  Next, the result of LTR landscape paper is shown.

表６から従来例ヒータ［４］のように、抵抗値の変化が小さいと端部の発熱量が高くなり、非通紙部昇温が高くなるので、スループットは低下する。また、逆に従来例ヒータ［５］のように抵抗値の変化が大きいと端部の発熱量が低くなり、スループットアップが実現できる。しかし、端部の発熱量を減らしている為、端部の定着性が満足できない。
以上の様に、通紙基準が端部基準の画像形成装置においても、中央基準と同様、スループットと定着性を満足させるには本実施例のように、所望の位置で発熱体の変化量を変化させる事で、他の部材を追加せずに、小サイズはもとよりＬＴＲのスループットアップ、定着性、ホットオフセットを両立する事が出来る。

From Table 6, as shown in the conventional heater [4], when the change in the resistance value is small, the amount of heat generated at the end portion becomes high, and the temperature rise at the non-sheet passing portion becomes high. On the contrary, if the resistance value is greatly changed as in the conventional heater [5], the amount of heat generated at the end becomes low, and the throughput can be increased. However, since the amount of heat generated at the end is reduced, the fixing property at the end cannot be satisfied.
As described above, even in an image forming apparatus in which the paper passing standard is the edge standard, in order to satisfy the throughput and the fixability as in the case of the central standard, the amount of change of the heating element is set at a desired position as in this embodiment. By changing it, it is possible to achieve both an increase in LTR throughput, fixability, and hot offset as well as a small size without adding other members.

Schematic diagram of an example of an image forming apparatus in Embodiment 1. Schematic diagram of fixing device (1) is a plan model diagram of the heater (heating body) surface side, (2) is a plan model diagram of the heater surface side with the surface protective layer removed, and (3) is a plan model diagram of the heater back side. Fig. 3 (3) (4)-(4) line section enlarged cross-sectional model view Block diagram of heater power supply control system Schematic of resistance heating element shape and heat distribution Schematic of other resistance heating element shapes and heat distribution Schematic of yet another resistance heating element shape and heat generation distribution Schematic diagram of resistance heating element shape and heat generation distribution of heater used in Example 2 Schematic of resistance heating element shape and heat distribution of conventional heater [1] Schematic diagram of resistance heating element shape and heat distribution of conventional heater [2] Schematic diagram of resistance heating element shape and heat distribution of conventional heater [3] Explanatory drawing of Example 3

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Laser scanner unit, 10 ... Process cartridge, 18 ... Fixing device, 23 ... Heater

Claims (16)

In a heating element used in a heating device having a substrate and a resistance heating element provided along the longitudinal direction of the substrate, and heating a material to be heated,
The substrate is provided with a plurality of resistance heating elements in the short direction of the substrate, and at least one resistance heating element has a region in which a resistance value per unit length varies in the longitudinal direction. A heating element characterized in that the amount of change in resistance value per unit length of the region where the resistance value changes is non-uniform in regions other than those corresponding to the safety element installation portion and the temperature detection element installation portion.   The combined resistance per unit length of the plurality of resistance heating elements on the substrate in the short direction of the substrate should be constant in the longitudinal direction in a region other than that corresponding to the safety element installation part and the temperature detection element installation part. The heating element according to claim 1.   The position where the amount of change in the resistance value of the at least one resistance heating element is non-uniform is provided symmetrically with respect to the approximate center in the longitudinal direction of the resistance heating element. The heating body according to 1.   The resistance value of the resistance heating element portion corresponding to the longitudinal width of the material to be heated having the minimum width that can be conveyed to the heating device is constant in a region other than that corresponding to the safety element installation portion and the temperature detection element installation portion with respect to the substrate. The heating body according to claim 1, wherein:   2. The resistance value of at least one of the plurality of resistance heating elements decreases from approximately the center in the longitudinal direction to the end or from one end to the other end in the longitudinal direction. Heating body.   2. The resistance value according to claim 1, wherein at least one of the plurality of resistance heating elements has a resistance value that increases from substantially the center in the longitudinal direction to the end portion or from one end portion to the other end portion in the longitudinal direction. Heating body.   The non-uniform position of the resistance value change amount of the resistance heating element is provided on the side of the longitudinal end from the end of the region corresponding to the longitudinal width of the minimum width material to be heated that can be conveyed to the heating device. The heating element according to claim 1. A heating element fixedly supported by a support, a safety element and a temperature detection element installed on a substrate of the heating element, a flexible member that moves while contacting the heating element, and the flexible member In a heating apparatus that includes a heating member and a pressure member that forms a nip, and heats the material to be heated while being nipped and conveyed at the nip portion.
The heating body includes a substrate whose longitudinal direction is the direction intersecting the heated material transport direction, and a plurality of resistance heating elements formed on the substrate along the longitudinal direction of the substrate and arranged in the heated material transport direction. Among the plurality of resistance heating elements, at least one resistance heating element has a region in which a resistance value per unit length varies between the conveyance reference of the material to be heated and the longitudinal end portion. The heating is characterized in that the amount of change in the resistance value per unit length of the region where the resistance value changes is non-uniform in the region other than that corresponding to the safety element installation portion and the temperature detection element installation portion with respect to the substrate. apparatus.   The combined resistance per unit length of the plurality of resistance heating elements on the substrate with respect to the heated material conveyance direction is constant in the longitudinal direction in a region other than the safety element installation part and the temperature detection element installation part. The heating apparatus according to claim 8, wherein:   The position where the amount of change in resistance value of the resistance heating element is non-uniform from the transport reference to the longitudinal end is provided symmetrically with respect to the transport reference. Heating device.   The resistance value of the resistance heating element is kept constant in the area other than the safety element installation part and the temperature detection element installation part with respect to the substrate from the conveyance reference to the longitudinal width end of the minimum material to be heated. The heating apparatus according to claim 8.   The heating device according to claim 8, wherein at least one of the plurality of resistance heating elements has a resistance value that decreases from the conveyance reference to a longitudinal end portion.   The heating device according to claim 8, wherein at least one of the plurality of resistance heating elements has a resistance value that increases from the conveyance reference to a longitudinal end portion.   The heating apparatus according to claim 8, wherein the conveyance reference is a central reference.   The heating apparatus according to claim 8, wherein the conveyance reference is an end reference.   From the conveyance reference to the longitudinal end portion, a non-uniform position of the resistance value change amount of the resistance heating element is provided on the longitudinal end side from the end portion of the smallest material to be heated that can be conveyed. The heating apparatus according to claim 8.

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