JP2018031869A - Pictorial image heating device, and heater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce waiting time during the execution of a printing job using large-size recording material following a printing job using small-size recording material thereby to enhance productivity.SOLUTION: A heater 600 for use in a pictorial image heating device 40 that heats a pictorial image T has a narrow and long base plate 610, and a first heat generator 701 and a second heat generator 702 formed in the longer side direction of the base plate with a space in-between in the shorter side direction, having the same greater side width A and each permitting heating by electricity independent of the other. The distribution of resistance in the longer side direction of the first heat generator 701 is uniform, and the distribution of resistance in the longer side direction of the second heat generator 702 is such that the resistance of a prescribed width area 702a corresponding to the width of recording material P is narrower than the resistance of an external area 702b corresponding to a prescribed width area.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image heating apparatus that heats an image on a recording material and a heater (heating body) used therefor. The image heating apparatus and the heater of the present invention can be used in an image forming apparatus such as a copying machine such as an electrophotographic system or an electrostatic recording system, a printer, a facsimile machine, or a multifunction machine having a plurality of these functions.

  Conventionally, a contact heating type heat roller system or a belt (film) heating system is generally employed for a fixing device as an image heating device applied to an image forming apparatus.

  In a belt heating type fixing device, a heat-resistant fixing belt (hereinafter referred to as a belt), which is a heating rotator, is pressure-bonded to a heater by a pressure roller, which is a pressing rotator, and is slid and conveyed. Then, a recording material (hereinafter referred to as paper) carrying an unfixed toner image is introduced into a fixing nip portion (hereinafter referred to as nip portion) formed by a pressure roller and a heater via a belt. It is transported with the belt. As a result, the unfixed toner image is fixed on the paper as a fixed image by the heat from the heater applied via the belt and the pressure applied to the nip portion.

  Since the belt heating type fixing device as described above can use a low heat capacity linear heating element as a heating element provided in the heater and a low heat capacity thin film as a belt, it can reduce power consumption and weight time ( (Quick start property) is possible.

  The present applicant has proposed a heater configuration of Patent Document 1 as a heater in a belt heating type fixing device. In this heater, a plurality of heating elements having different lengths in the longitudinal direction are arranged in parallel along the short direction on the insulating substrate, and the length in the longitudinal direction is short on the upstream side in the width direction of the insulating substrate in the recording material traveling direction. The heating element is arranged.

  This heater selects the heating element to be energized according to the width size of the paper to be passed, and when passing a wide large size paper, the length in the longitudinal direction is long and the width is long. A wide heating element generates heat. When passing a small-sized sheet having a width equal to or less than a certain amount, a heating element having a short length in the longitudinal direction and a narrow width is caused to generate heat. As a result, the temperature rise in the non-sheet passing portion area of the sheet is suppressed, and the productivity of small size sheets is satisfied. Further, it is described that in a fixing device for fixing papers of various width sizes, the amount of heat required differs depending on the paper width size, and it is desirable to change the amount of heat generation according to the paper width size.

  In the above, the reason for not controlling (switching) the long and wide heating element and the short and narrow heating element during printing is as follows. Since the heater system generates heat independently, the energization amount (electric power amount) energized to each heating element increases, and the variation in energization current during control increases. When the energization current increases, when switching between a long and wide heating element and a short and narrow heating element, flicker is used for phase control and harmonic is used for wave number control. Noise phenomenon due to wave distortion occurs.

JP 2001-194936 A

  In the heater disclosed in Patent Document 1, when passing a wide and large size sheet, the lengthwise length is long, the wide heating element is heated, and the small size sheet having a width of a certain amount or less is passed. When heating, a heating element having a short length in the longitudinal direction and a narrow width is caused to generate heat. Therefore, the two heating elements are not controlled (switched) during the sheet passing. That is, only small-size heating elements generate heat in small-size paper.

  Therefore, when printing a large size paper after printing a small size paper, it extends from the end of the small size heating element to the non-sheet passing portion (the end of the small size heating element to the end of the substrate) to the belt. It will weaken the way heat is transmitted. As a result, a time (wait time) for warming the belt is required before printing a large-size sheet which is the next print job (Job), which causes a problem that productivity as a whole is reduced.

  The present invention is a further development of the technique of Cited Document 1. An object of the present invention is to provide an image heating apparatus and a heater capable of reducing the wait time when printing a large size recording paper after printing a small size recording material and improving productivity.

  In order to achieve the above object, a typical configuration of the image heating apparatus according to the present invention includes a heater, a heat transfer member that moves while sliding in contact with the heater, and the heat transfer between the heater. An image that heats an image on the recording material by nipping and conveying the recording material at a nip portion formed between the heat transfer member and the nip forming member. In the image heating apparatus having a peak of pressure on the downstream side of the central portion of the heater in the short-side direction with respect to the recording material conveyance direction in the nip portion, the heater includes an elongated substrate, A first substrate that is arranged in parallel with a gap between the upstream side and the downstream side with respect to the recording material conveyance direction in the nip portion in the short side direction of the substrate along the longitudinal direction of the substrate and that can generate heat independently by energization. Heating element And a second heating element, the resistance distribution along the length of the first heating element is substantially uniform, and the resistance distribution along the length of the second heating element has a predetermined recording material width. The resistance distribution of the outer region of the predetermined width region is lower than the corresponding resistance of the predetermined width region.

  A typical configuration of a heater according to the present invention for achieving the above object is as follows: a heater, a heat transfer member that moves while sliding in contact with the heater, and the heat transfer member between the heaters. An image heating apparatus that heats an image on the recording material by sandwiching and conveying the recording material at a nip portion formed between the heat transfer member and the nip forming member The heater used in the image heating apparatus having a peak of pressure on the downstream side of the central portion in the short-side direction of the substrate with respect to the conveyance direction of the recording material in the nip portion, and an elongated substrate; The substrate is arranged in parallel with a gap between the upstream side and the downstream side along the longitudinal direction of the substrate and with respect to the recording material conveyance direction in the nip portion in the short side direction of the substrate. 1 A heating element and a second heating element, wherein the resistance distribution along the length of the first heating element is substantially uniform, and the resistance distribution along the length of the second heating element is a predetermined recording material. The resistance distribution is such that the resistance of the outer region of the predetermined width region is lower than the resistance of the predetermined width region corresponding to the width.

  According to the present invention, an image heating apparatus and a heater that can reduce the amount of heat necessary for heating an image, reduce the wait time when printing a large size recording material after printing a small size recording material, and improve productivity. Can be provided.

The schematic diagram of the principal part of the heater of Example 1 Schematic diagram of the main part of the heater and power supply system diagram Explanatory drawing of the formation point of the 2nd heating element of the heater Explanatory drawing of belt longitudinal temperature distribution of the fixing device using the heater of the embodiment and the fixing device using the heater of the comparative example Contact pressure (pressing force) distribution in the short nip direction Schematic of the main part of the heater of the comparative example FIG. 6 is a diagram illustrating sheet passing and standby timings of a fixing device using a heater of an embodiment and a fixing device using a heater of a comparative example. (A) is a schematic cross-sectional view of the main part of the fixing device of the embodiment, and (b) is a schematic diagram of a layer structure of the fixing belt. Longitudinal front view of the main part of the fixing device Schematic diagram of configuration of image forming apparatus in embodiment Explanatory drawing of the formation point of the 2nd heat generating body of the heater of Example 2. FIG. Furthermore, the schematic diagram of the principal part of the heater of another Example.

  Embodiments according to the present invention will be described below. In the following embodiments, a laser beam printer using an electrophotographic process will be described as an example of an image forming apparatus.

Example 1
[Image forming apparatus]
FIG. 9 is a schematic sectional view of the printer 1 in this embodiment. The printer 1 is a tandem-intermediate transfer type full-color printer, which is an image of toners of yellow (Y), magenta (M), cyan (C), and black (Bk) colors (hereinafter, toner images). ) Has four image forming portions UY, UM, UC, and UBk.

  Each image forming unit includes a photosensitive drum 2, a charger 3, a laser scanner 4, a developing device 5, a primary transfer charger 6, and a drum cleaner 7. In order to avoid complication of the drawing, the reference numerals for these devices in the image forming units UM, UC, and UBk other than the image forming unit UY are omitted. Further, since the electrophotographic process and image forming operation of these image forming units are known, the description thereof is omitted.

  The toner images of the respective colors are primarily transferred onto the intermediate transfer belt 8 that is rotated from the drum 2 of each image forming unit in a predetermined manner. As a result, a four-color superimposed toner image is formed on the belt 8. On the other hand, a recording material (sheet: hereinafter referred to as paper) P is fed to one sheet from the cassette 9 or 10 or the manual feed tray 11, passes through the conveyance path 12, and the belt 8 and the secondary transfer roller at a predetermined control timing. 13 is introduced into the secondary transfer nip portion, which is a pressure contact portion with 13. As a result, the four-color superimposed toner images on the belt 8 are secondarily transferred to the paper P at a time. The paper P is introduced into the fixing device 40 and undergoes toner image fixing processing.

  In the single-sided image forming mode, the paper P exiting the fixing device 40 is guided to the transport path 15 side by the control of the flapper 14 and is discharged face down on the discharge tray 16. Alternatively, it is guided to the transport path 17 side and discharged onto the discharge tray 18 face up.

  In the double-sided image forming mode, the paper P exiting the fixing device 40 is once guided to the transport path 15 by the control of the flapper 14, then switched back and introduced to the double-side transport path 19. Then, in a state where the front and back sides are reversed, the toner image is again formed on the other surface through the conveyance path 12 and introduced into the secondary transfer nip portion. Thereafter, it is introduced into the fixing device 40 as in the case of single-sided image formation, and discharged to the discharge tray 16 or 18 as a double-sided image formed product.

  In the printer 1 of the present embodiment, the conveyance of the paper P of various large and small width sizes is performed based on a so-called central reference at the center of the paper width. In the following, the maximum width size paper that can be used in the apparatus is referred to as a large size paper, and the narrower width paper is referred to as a small size paper.

[Fixing device]
Next, the fixing device 40 in this embodiment will be described. FIG. 7A is a schematic cross-sectional view of the main part of the fixing device 40, and FIG. 7B is a schematic diagram of the layer structure of the fixing belt. FIG. 8 is a schematic longitudinal sectional front view of the main part of the fixing device 40 with the middle part omitted. The front surface of the fixing device 40 is a surface viewed from the paper introduction side.

  The fixing device 40 is a belt (film) heating type image heating device. Broadly speaking, a belt unit (film unit) 60 that heats an image on a sheet (on a recording material), an elastic pressure roller 70 as a counter member (nip forming member), and an apparatus housing 41 that accommodates them. And having.

  The belt unit 60 is configured to heat a flexible thin fixing belt (fixing film: hereinafter referred to as a belt) 603 in the form of an endless belt as a heat transfer member by a heater 600 that contacts the inner surface of the belt. Therefore, the belt 603 can be heated efficiently and the start-up performance is excellent. A nip portion (fixing nip portion) N is formed on the belt 603 by the pressure of the heater 600, the heater holder 601, and the pressure roller 70, and the paper P fed to the nip portion N is nipped and conveyed. At this time, the heat generated by the heater 600 is applied to the paper P via the belt 603, and the toner image T on the paper P is fixed to the paper P.

  The belt unit 60 is a unit for heating and pressing the image on the paper P, and is provided so as to be substantially parallel to the pressure roller 70. The heater (heating body) 600, the heater holder 601, the support stay 602, and the belt 603 are provided. Have The belt 603 is loosely fitted around the outer assembly of the heater (heating body) 600, the heater holder 601, and the support stay 602.

  The heater 600 presses the belt 603 in the direction of the pressure roller 70 so that the nip portion N has a desired width in the paper conveyance direction (recording material conveyance direction) a. The heater 600 includes a substrate 610, and first and second resistance heating elements (resistance heating layers: hereinafter referred to as heating elements) 701 and 702 that generate heat when energized on the substrate 610. It is fixed to the recess 601a.

  As shown in FIG. 7A, the heater holder 601 is configured such that the height of the convex portion (jaw portion) 601b on the downstream side in the recording material conveyance direction a is set to the height of the convex portion on the upstream side with respect to the concave portion 601a on the lower surface for fixing the heater 600. (Jaw part) It is made higher than the height of 601c.

  Specifically, the heights of the convex portions 601c and 601b on the upstream side and the downstream side in the recording material conveyance direction a are respectively determined from the surfaces contacting the inner side of the fixing belt 603 of the heater 600 fixed to the concave portion on the lower surface. , 0 μm and 350 μm in height. As a result, the peak of the pressing force is given to the downstream side of the central portion of the heater 600 in the short side direction of the substrate with respect to the recording material conveyance direction a in the nip portion N.

  In this embodiment, the first and second heating elements 701 and 702 are provided on the back side of the substrate 610 (the side not in contact with the belt 603). However, the present invention is not limited to this, and may be provided on the surface side (side contacting the belt 603). The detailed configuration of the heater 600 will be described in detail in the section [Heater].

  The belt 603 is a flexible thin cylindrical member that heats and pressurizes the toner image T on the paper P at the nip portion N. In this embodiment, as shown in the schematic diagram of the layer structure in FIG. 7B, a substrate provided with an elastic layer 603b and a release layer 603c on a base material 603a is used. Specifically, as the base material 603a, a cylindrical member made of a nickel alloy having an outer diameter of 30 mm, a length (width) of 340 mm, and a thickness of 30 μm is used. Furthermore, a silicone rubber layer having a thickness of 400 μm is formed as an elastic layer 603b on the base material 603a, and a fluororesin tube having a thickness of about 20 μm is coated as a release layer 603c on the elastic layer 603b.

  The heater holder 601 (hereinafter referred to as the holder 601) is a member that holds the heater 600 in a state of being pressed toward the belt 603. Further, the holder 601 has a substantially semicircular cross-sectional shape and has a function of regulating the rotation trajectory of the belt 603. The holder 601 is made of highly heat-resistant resin or the like, and in this embodiment, Zenite 7755 (trade name) manufactured by DuPont is used.

  The support stay 602 is a member that supports the heater 600 via the holder 601. The support stay 602 is desirably made of a material that is not easily bent even when a large load is applied. In this embodiment, SUS304 (stainless steel) is used.

  As shown in FIG. 8, the support stay 602 is supported by the flanges 411a and 411b at both ends in the longitudinal direction. The flanges 411a and 411b are collectively referred to as a flange 411. The flange 411 regulates the movement of the belt 603 in the longitudinal direction and the shape in the circumferential direction. A heat-resistant resin or the like is used for the flange 411, and PPS (polyphenylene sulfide) is used in this embodiment.

  The flanges 411 (a, b) are engaged with guide slits 43 (a, b) provided in the side plates 41 (a, b) on one end side and the other end side of the apparatus housing 41, respectively, and press rollers It has a degree of freedom to slide in a direction approaching 70 and a direction away from it. A pressure spring 415 (a, b) is provided in a contracted state between the flange 411 (a, b) and the pressure arm 414 (a, b).

  With the above configuration, the elastic force of the pressure spring 415 is transmitted to the heater 600 through the flange 411, the support stay 602, and the holder 601. The belt 603 is pressed against the pressure roller 70 with a predetermined pressing force by a part of the heater 600 and the holder 601, and a nip having a predetermined width is formed between the belt 603 and the pressure roller 70 in the sheet conveyance direction a. Part N is formed. The applied pressure in this embodiment is about 156.8 N on one end side and the other end side, respectively, and the total applied pressure is about 313.6 N (32 kgf).

  The connector 500 is a power supply member that is electrically connected to the heater 600 in order to apply a voltage to the heater 600, and is detachably attached to one end in the longitudinal direction of the heater 600.

  The pressure roller 70 is a driving rotary member that forms a nip portion N for heating the toner image T on the paper in cooperation with the belt 603 and that drives the belt 603 to rotate. The pressure roller 70 has a multilayer structure in which an elastic layer 72 is provided on a metal core 71 and a release layer 73 is provided on the elastic layer 72. As the metal core 71, stainless steel, SUM (sulfur and sulfur composite free-cutting steel), or aluminum can be used. As the elastic layer 72, silicone rubber, sponge rubber layer, or elastic foam rubber can be used. As the release layer 73, a fluororesin material can be used.

  The pressure roller 70 of this embodiment comprises a stainless steel core 71, an elastic layer 72 of foamed silicone rubber, and a release layer 73 of a fluororesin tube. The outer diameter is about 25 mm, and the longitudinal length of the elastic layer is 330 mm.

  As shown in FIG. 8, both end portions of the metal core 71 of the pressure roller 70 rotate between bearings 41 (a, b) between one end side and the other end side plates 41 a, 41 b of the apparatus housing 41. Held possible. A gear G is provided at one end of the core bar 71 to transmit the driving force of the motor (drive source) M controlled by the control circuit (control unit) 100 to the core bar 71.

  The pressure roller 70 driven by the motor M rotates in the direction of the arrow R70 in FIG. 7, and the driving force is transmitted to the belt 603 at the nip portion N to cause the belt 603 to be driven to rotate in the direction of the arrow R603. The belt 603 is rotated by the rotation of the pressure roller 70 while the inner surface of the belt 603 slides in close contact with the lower surface of the heater 600 and a part of the surface of the holder 601 at the nip portion N. In this embodiment, the motor M is controlled by the control circuit 100 so that the surface speed of the pressure roller 70 is 200 mm / sec.

  As described above, the pressure roller 70 is rotationally driven by the drive of the motor M, and the belt 603 is driven to rotate accordingly. Then, as will be described later, energization control for the heater 600 is performed, and the heat generation area of the heater 600 is raised to a predetermined temperature and the temperature is adjusted.

  In this fixing device state, the paper P carrying the unfixed toner image T is introduced into the fixing device 40 from the image forming unit side, enters the nip portion N, and is nipped and conveyed. As a result, the toner image is fixed to the recording material by heating and pressing at the nip portion N. The sheet P that has passed through the nip portion N is separated from the surface of the belt 603 and is discharged and conveyed.

[heater]
Next, the configuration of the heater 600 will be described in detail. FIG. 2A is a schematic plan view on the back side of the heater 600 and a block diagram of a power feeding system in the present embodiment. (B) of the same figure is an enlarged cross-sectional schematic diagram of the heater 600 of (a) as seen from the arrow (b)-(b). FIG. 1 is a schematic plan view of the back side of the heater without the insulating coating layer 704 and the temperature sensor TH. In addition, the figure is a schematic diagram, and the dimension ratio of the constituent member / part in the figure does not correspond to the dimension of the constituent member / part described below.

  The heater 600 has an elongated insulating substrate 610. The substrate 610 is a member that determines the size and shape of the heater 600 and is a member that can contact the inner surface of the belt along the longitudinal direction (width direction) of the belt 603. As the material of the substrate 610, a ceramic material such as alumina or aluminum nitride having excellent heat resistance, thermal conductivity, electrical insulation, and the like is used. In this embodiment, an alumina nitride plate member having a length in the longitudinal direction of about 400 mm, a length in the short side direction of about 10 mm, and a thickness of about 1 mm is used.

  The side of the substrate 610 that contacts the inner surface of the belt 630 is the front side, and the opposite side is the back side. On the surface side of the substrate 610, for example, a polyimide layer having a thickness of about 10 μm may be provided as a sliding layer 703 in the contact surface area with the belt inner surface. By providing the sliding layer 703, it is possible to reduce the rubbing resistance between the belt 630 and the heater 600 and suppress wear on the inner surface of the belt. In order to further improve the slidability, a lubricant such as grease may be applied to the inner surface of the belt.

  A plurality of heating elements substantially parallel to each other are formed on the back side of the substrate 610 along the longitudinal direction of the substrate and spaced apart in the lateral direction of the substrate. Is formed. In the present embodiment, the first side that is arranged in parallel with a gap between the upstream side and the downstream side with respect to the paper conveyance direction (recording material conveyance direction) a in the nip portion N in the short side direction of the substrate along the longitudinal direction of the substrate. A heating element 701 and a second heating element 702 are included.

  In FIG. 1, XX is a center line (bisector: imaginary line) having a short width of the substrate. The first heating element 701 is disposed at a position substantially corresponding to the center line XX. The second heating element 702 is disposed at a predetermined distance from the first heating element 701 on the downstream side in the paper conveyance direction (hereinafter referred to as the nip downstream side).

  In addition, three electrodes of a common electrode 711, a first individual electrode 712, and a second individual electrode 713 are formed on one end side in the substrate longitudinal direction on the back surface side of the substrate 610. The common electrode 711 is electrically connected to each other end side of the first and second heating elements 701 and 702 opposite to the one end side which is the common electrode 711 side via the common power supply wiring 711a. ing. The first and second individual electrodes 712 and 713 are respectively connected to the individual electrodes 712 and 713 of the first and second heating elements 701 and 702 via the first and second individual power supply wirings 712a and 713a, respectively. It is electrically connected to a certain one end side.

  The entire common electrode 711, first individual electrode 712, second individual electrode 713, common power supply wiring 711a, first individual power supply wiring 712a, and second individual power supply wiring 713a are referred to as a conductor pattern or a wiring.

  Each of the heating elements 701 and 702 and the conductor pattern can be formed by a thick film printing method (screen printing method) using, for example, a conductive thick film paste. In this embodiment, silver paste is used for the conductor pattern so that the resistivity is low. The resistance value of the conductor pattern is about 0.005Ω. A silver-palladium alloy paste is used for the heating elements 701 and 702 so as to increase the resistivity. The resistance values of the heating elements 701 and 702 will be described later.

  As shown in FIG. 2, the heating elements 701 and 702 and the portions of the conductor pattern excluding the common electrode 711, the first individual electrode 712, and the second individual electrode 713 are insulating coatings made of heat-resistant glass. Covered by layer 704. The insulating coat layer 704 electrically protects the heating elements 701 and 702 and the conductor pattern portion so as not to cause a leak or a short circuit.

  Further, a thermistor TH as a temperature sensor for detecting the heater temperature is adhered to the surface of the insulating coating layer 704 on the back surface side of the substrate 610 or is pressed by a pressing force of a pressing member (not shown). Has been. In the printer 1 of the present embodiment, the conveyance of the paper P is performed based on the center as described above. Therefore, the thermistor TH is disposed at a position substantially corresponding to the central reference line OO (virtual line) for paper conveyance so as to detect the temperature of the heater portion corresponding to the substantially central portion of the heating elements 701 and 702 in the longitudinal direction. ing.

  The thermistor TH is connected to the control circuit 100 via the cable 705 and the A / D converter 706, and transmits an output corresponding to the detected temperature to the control circuit 100. The control circuit 100 is a circuit that includes a CPU that performs operations associated with various controls, and a non-volatile storage medium such as a ROM that stores various programs. A program is stored in the ROM, and various controls are executed by the CPU reading and executing the program. The control circuit 100 may be an integrated circuit such as an ASIC as long as the same function is achieved.

  A connector 500 which is a power supply member electrically connected to the heater 600 to apply a voltage to the heater 600 is provided with a common electrode 711, a first individual electrode 712, and a second individual electrode 713 of the heater 600. It is detachably attached to one end side.

  In a state where the connector 500 is mounted, the common electrode 711 is connected to a terminal 200a on one side of the power supply unit 200 that is a power supply source for supplying power to the heater 600 via the cable 501 and the switch (relay) SW502. The first individual electrode 712 is connected to the terminal 200b on the other side of the power supply unit 200 via the cable 503 and the switch SW504. The second individual electrode 713 is connected to the terminal 200b on the other side of the power supply unit 200 via the cable 505 and the switch SW506.

  The switches SW502, SW504, and SW506 are selectively on / off controlled by the control circuit 100, respectively. When the switches SW502 and SW504 are turned on, a voltage is applied between one end side and the other end side of the first heating element 701, and the first heating element 701 generates heat over the entire length region. Further, when the switches SW502 and SW506 are turned on, a voltage is applied between one end side and the other end side of the second heating element 702, and the second heating element 702 generates heat over the entire length region.

  That is, the first and second heating elements 701 and 702 can generate heat independently by energization. The control circuit unit 100 selectively causes the first heating element 701 and the second heating element 702 to generate heat according to the width size of the paper P introduced into the fixing device 40. This will be described later.

  The control circuit 100 is electrically connected to the power supply unit 200 so as to control the energization content of the power supply unit 200. The control circuit 100 reflects the detected temperature information acquired (input) from the thermistor TH in the energization control of the power supply unit 200. That is, the control circuit 100 controls the power supplied to the first heating element 701 or the second heating element 702 of the heater 600 via the power supply unit 200 based on the output of the thermistor TH.

  In this embodiment, the control circuit 100 adjusts the heat generation amount of the heater 600 by performing wave number control of the output of the power supply unit 200. By performing such control, the sheet passing area portion of the heater 600 is raised to a predetermined temperature for fixing (205 ° C. in the present embodiment) and maintained almost constant. In this embodiment, a commercial AC power supply having a single-phase AC effective value of about 100 V is used as the power supply unit 200. The power source unit 200 may be a DC power source as long as it has a function of supplying power to the heater 600.

  In the heater 600 of this embodiment, the first and second heating elements 701 and 702 are both formed by patterning by applying an Ag / Pd resistance material with a thickness of about 10 μm. The first and second heating elements 701 and 702 both use a heating element having a longitudinal width A of 322 mm. This longitudinal width A: 322 mm is a length corresponding to the vertical width (320 mm) of SRA3 as the maximum width size paper (large size paper) that can be used in the image forming apparatus (printer) or fixing device of this embodiment. is there.

  The first heating element 701 that is the heating element on the upstream side of the nip has a substantially uniform resistance distribution per unit area over the entire length of the longitudinal width A of 322 mm. A resistance value within ± 5% may be used as a substantially uniform range of the resistance distribution. Thus, if the resistance value is substantially uniform, there is almost no influence on the longitudinal temperature distribution. In this embodiment, the resistance value per unit area of the first heating element 701 is 7Ω.

  Regarding the second heating element 702 which is a heating element on the downstream side of the nip, the resistance distribution per unit area is changed within the longitudinal width A: 322 mm. Specifically, the second heating element 702 includes a central portion (predetermined width region) 702a corresponding to a paper passing region of a paper (small size paper) that is narrower than the maximum width size paper, and an outer side thereof. The resistance distribution per unit area is changed with the end portion (outer region) 702b corresponding to the non-passing region.

  In this embodiment, A4 landscape (width 297 mm) is assumed as a paper having a predetermined width smaller than the maximum width size paper, and with respect to the second heating element 702, the longitudinal width of the central portion 702a is 301 mm. The longitudinal width of the end portion 702b is 10.5 mm. The resistance value per unit area in the central portion 702a of the second heating element 702 is set to 7Ω, which is the same as the resistance value per unit area of the first heating element 701.

  On the other hand, the resistance value per unit area of the end portion 702b is smaller than the resistance value per unit area in the central portion 702a. In this embodiment, since the resistance ratio between the resistance value per unit area of the end portion 702b and the resistance value of the central portion 702a is 1: 5, the resistance value of the end portion 702b is in the range of 1.4 ± 5% Ω. It is made smaller than the resistance value of 702a. By doing so, the amount of heat generated at the end 702b can be aimed.

  The control circuit unit 100 turns on the switches SW502 and SW504 to cause the first heating element 701 to generate heat when the width of the sheet introduced into the apparatus is a large size sheet having a width larger than 297 mm on the side of A4. The second heating element 702 does not generate heat. If the paper introduced into the apparatus is a small-size paper whose width is equal to or less than the width of A4 (297 mm or less), the switches SW502 and SW506 are turned on to cause the second heating element 702 to generate heat. The first heating element 701 does not generate heat.

  The reason why the heater is configured as described above is that the amount of power input to the central portion 702a of the second heating element 702 is increased when the A4 landscape (width 297 mm) sheet is frequently fed due to the usage ratio of the image forming apparatus. It becomes possible. Therefore, since the heat generation amount of the end portion 702b is reduced while satisfying the fixability of the A4 portion, the temperature rise of the non-sheet passing portion can be reduced.

  Further, the first and second heating elements 701 and 702 are also characterized by the arrangement in the heater substrate width direction. The second heat generating element 702 whose resistance distribution in the longitudinal width of the heat generating element is changed is arranged with respect to the first heat generating element 701 on the downstream side in the sheet feeding direction and the fixing nip (on the downstream side of the nip).

  The reason for this is that when the A4 landscape (width 297 mm) sheet is frequently fed due to the usage ratio of the image forming apparatus, the rear end of the nip portion is pressed and fixed as a peak pressure. Thus, it is desirable that the second heating element 702 is disposed on the downstream side where the toner is sufficiently heated and the fixing property is most easily satisfied. In other words, by giving a peak of pressure at the rear end of the nip part, it is possible to reduce the amount of heat necessary for image fixing while maintaining the fixability at the rear end of the nip part where the toner is sufficiently heated. Yes.

  In this embodiment, the resistance value per unit area of the end portion 702b of the second heating element 702 is made smaller than that of the central portion 702a by the method as shown in the schematic diagram of FIG. That is, the first and second heating elements 701 and 702 are coated on the aluminum nitride substrate (insulating substrate) 610 of the heater 600 with an Ag / Pd resistance material having a thickness of about 10 μm (one coating). At that time, five layers (five times) are applied at the position (position) of the end portion 702b of the second heating element 702. By doing so, it becomes possible to reduce the resistance value per unit area of the coating portion of the end portion 702b from 7Ω of the central portion 702a to 1.4Ω.

  That is, the resistance value per unit area between the central portion 702a and the end portion 702b of the second heating element 702 is changed depending on the thickness of the heating element.

  Next, the A4 paper (small size paper) in this embodiment was continuously passed for 1 minute, and the paper passing time when the SRA3 paper (large size paper) was printed (1 minute) was compared.

  First, the temperature distribution in the longitudinal direction of the belt 603 when an A4 sheet is continuously passed for 1 minute will be described. FIG. 4 is a diagram showing a temperature distribution related to the longitudinal direction position of the heating element of the belt 603 when the heater 600 of this embodiment and the heater 600A of the comparative example shown in FIG. 5 are used. The temperature distribution when the heater 600 of this embodiment is used is indicated by a solid line, and the temperature distribution when the heater 600A of a comparative example is used is indicated by a broken line.

  In the heater 600A of the comparative example of FIG. 5, the end portion 702b is removed from the second heating element 702 in the heater 600 of the first embodiment of FIGS. 1 and 2, and only the central portion 702a is formed. Further, the first heating element 701 is arranged on the nip downstream side, and the second heating element 702 is arranged on the nip upstream side. The heater 600A of this comparative example has a configuration corresponding to the heater configuration described in Patent Document 1.

  The horizontal axis in FIG. 4 is based on the left end of the first and second heating elements 701 and 702 of the heaters 600 and 600A in FIGS. In the fixing device of the present embodiment, the temperature at the central portion in the longitudinal direction of the heater 600 is maintained at 205 ° C. by the thermistor TH as described above.

  At this time, in the case where the sheet is continuously passed for 1 minute, the heater 600A of the comparative example generates heat only from the A4 width heating element portion 702a, so the temperature of the belt 603 from the A4 width to the non-sheet passing portion region is low. . On the other hand, in the heater configuration of this embodiment, in addition to the A4 width heating element portion 702a, the heat generation amount itself is low even from the A4 width to the non-sheet passing portion region 702b, but the heater generates heat. Therefore, the temperature of the belt 603 from the A4 width heating element portion 702a to the non-sheet passing portion region 702b is higher than that in the comparative example.

  Therefore, it is easy to secure the temperature necessary for fixing the SRA3 paper (large size paper) which is the next print job (Job). As a result, the switching time to SRA3 paper or the like (large size paper) printing after A4 paper printing was required for 10 seconds in the heater 600A of the comparative example, whereas the switching time of 2 seconds was required in the heater 600 of this embodiment. It was OK. Therefore, as shown in FIG. 6, the heater 600 of this embodiment can be shortened by 8 seconds compared to the heater 600 </ b> A of the comparative example.

  In addition, as shown in FIG. 4A, the fixing force at the rear end of the nip portion where the toner is sufficiently heated is maintained by causing the peak of the applied pressure at the rear end of the nip portion (downstream of the nip portion N in the sheet conveyance direction). However, the amount of heat required for fixing can be reduced. Therefore, even when the belt surface temperature was lowered as compared with the comparative example, the fixing ability equivalent to that of the comparative example was obtained (FIG. 6).

  In the heater 600 of this embodiment, the heating element is composed of two elements, the first and second heating elements 701 and 702, and the resistance distribution of the second heating element 702 is expressed as Ag / Pd thickness. In other words, it has two regions of a central portion 702a and an end portion 702b. However, the present invention is not limited to this configuration, and it goes without saying that the present invention can also be applied to a configuration in which there are three or more heating elements and a resistance distribution obtained by changing the thickness of Ag / Pd has three or more regions.

  In this way, the heater 600 is provided with a non-sheet-passing heating element that selects an optimum heating element according to the width size of the paper introduced into the apparatus and generates a small amount of heat. It is possible to provide a fixing device that can shorten the switching time required for printing on paper.

Example 2
In the heater 600 according to the first embodiment, the resistance value per unit area between the central portion 702a and the end portion 702b of the second heating element 702 is changed depending on the thickness of the heating element. In the second embodiment, the resistance value per unit area between the central portion 702a and the end portion 702b of the second heating element 702 is changed depending on the material of the heating element. Other heater configurations, fixing device configurations, and image forming apparatus configurations are the same as those in the first embodiment, and a description thereof will be omitted.

  The configuration of the second heating element 702 in the heater 600 of the second embodiment will be described with reference to FIG. In the present embodiment, the second heat generating element 702 has a resistance distribution per unit area divided into a central portion 702a and an end portion 702b in the same manner as the second heat generating element 702 in the heater 600 of the first embodiment. The central portion 702a has the same resistance (7Ω) per unit area as the first heating element 701 and has a longitudinal width of 301 mm. The end portion 702b has a smaller resistance (1.4Ω) per unit area than the central portion 702a and has a longitudinal width of 10.5 mm.

  Also in the second embodiment, since the resistance ratio of the resistance value of the end portion 702b and the resistance value of the center 702a is 1: 5, the resistance value of the end portion 702b is 1.4 ± 5% Ω in the range of the center 702a. It is made smaller than the resistance value.

  The first and second heating elements 701 and 702 of the heater 600 are coated with an Ag / Pd resistance material with a thickness of about 10 μm (one coating) on an aluminum nitride substrate (insulating substrate) 610. In this case, at the end portion 702b of the second heating element 702, the mixing ratio of Ag / Pa is changed to the mixing ratio of Ag / Pa for forming the central part 702a and the first heating element 701. It is a method of coating the resistance material that has changed. By doing so, it becomes possible to reduce the resistance value per unit area of the coating portion of the end portion 702b from 7Ω of the central portion 702a to 1.4Ω.

  Since the fixing device using the heater 600 of the present embodiment is similar to the fixing device of the first embodiment, the switching time to SRA3 paper (large size paper) printing after A4 paper printing is OK in 2 seconds. It became possible to shorten it for 8 seconds compared with (Fig. 6).

  Further, as shown in FIG. 4A, by giving a peak of pressure at the rear end of the nip part, the heat amount necessary for fixing is lowered while maintaining the fixability at the rear end of the nip part where the toner is sufficiently heated. Can do. Therefore, even when the belt surface temperature was lowered as compared with the comparative example, the fixing ability equivalent to that of the comparative example was obtained (FIG. 6).

  Needless to say, the heater 600 of the present embodiment is also applicable to a configuration in which there are three or more heating elements and a resistance distribution obtained by changing the mixing ratio of Ag / Pd has three or more regions. .

  As described above, the fixing device capable of shortening the switching time required for printing from small-size paper to large-size paper can also be provided by the heater 600 of this embodiment.

<< Other Examples >>
1) Although the embodiments to which the present invention can be applied have been described above, the numerical values such as dimensions exemplified in the respective embodiments are merely examples, and are not limited to these numerical values. As long as the invention can be applied, numerical values can be selected as appropriate. Moreover, you may change suitably the structure as described in an Example in the range which can apply invention.

  2) As the shape of the second heating element 702 of the heater 600, the Ag / Pd thickness and the mixing ratio of the second heating element 702 of the heater 600 are not changed as in the first and second embodiments. It may be as follows. That is, the width of the second heating element 702 in the sheet passing direction (the substrate short direction) may be changed so that the end portion 702b is wider than the central portion 702a.

  3) The heat generation area of the heater 600 is not limited to the center reference. For example, the heat generation area of the heater 600 may be used as an end reference. Therefore, when the heat generation area of the small size paper is changed to the large heat generation area, the heat generation area on both ends of the small size paper is not enlarged, but the heat generation area on one end side of the small size paper is enlarged. Also good.

  4) The pattern of the heat generation area of the heater 600 is not limited to two patterns of large size and small size. For example, you may have the heat_generation | fever area | region of 3 or more patterns.

  5) The belt 603 is not limited to a configuration in which the inner surface thereof is supported by the heater 600 and driven by the roller 70. For example, it may be a unit system that is spanned by a plurality of rollers and driven by one of the plurality of rollers. However, the configurations as in the first and second embodiments are desirable from the viewpoint of reducing the heat capacity.

  6) The nip forming member that forms the nip portion N with the belt 603 is not limited to the roller member such as the roller 70. For example, a pressure belt unit in which a belt is stretched around a plurality of rollers may be used.

  7) The image forming apparatus described using the printer 1 as an example is not limited to an image forming apparatus that forms a full-color image, and may be an image forming apparatus that forms a monochrome image. Further, the image forming apparatus can be implemented in various applications such as a copying machine, a FAX, and a multi-function machine having a plurality of these functions in addition to necessary equipment, equipment, and housing structure.

  8) The image heating apparatus in the above description is not limited to an apparatus that fixes an unfixed toner image on the sheet P. For example, a device that fixes a semi-fixed toner image on the recording material P or a device that heats a fixed image may be used. Therefore, the fixing device 40 as the image heating device may be a surface heating device that adjusts the gloss and surface properties of the image, for example.

  40 .. Image heating device (fixing device), 600 .. Heater, P .. Recording material, T .. Image, 610 .. Substrate, 701 .. First heating element, 702 .. Second heating element, 702a... Predetermined width region, 702b .. Outer region

Claims (17)

A heater, a heat transfer member that moves while sliding in contact with the heater, and a nip forming member that contacts the heater with the heat transfer member interposed therebetween, the heat transfer member and the nip An image heating apparatus that heats an image on a recording material by sandwiching and conveying the recording material at a nip portion formed between the forming member and a substrate short direction of the heater with respect to the recording material conveyance direction in the nip portion In an image heating apparatus having a pressure peak downstream of the central part of
The heaters are juxtaposed on the long substrate and the substrate along the longitudinal direction of the substrate and spaced upstream and downstream with respect to the recording material conveyance direction in the nip portion in the short-side direction of the substrate. A first heating element and a second heating element that can generate heat independently, the resistance distribution along the length of the first heating element is substantially uniform, and the length of the second heating element is The image heating apparatus according to claim 1, wherein the resistance distribution along the line is a resistance distribution in which the resistance in the outer region of the predetermined width region is lower than the resistance in the predetermined width region corresponding to the width of the predetermined recording material.   The image heating apparatus according to claim 1, wherein the resistance in the predetermined width region and the resistance in the outer region are changed depending on the thickness of the heating element.   The image heating apparatus according to claim 1, wherein the resistance in the predetermined width region and the resistance in the outer region are changed depending on a material of the heating element.   The image heating apparatus according to claim 1, wherein the resistance in the predetermined width region and the resistance in the outer region are changed depending on a short width of the heating element.   5. The image heating apparatus according to claim 1, wherein the first heating element and the second heating element have the same resistance value per unit area of the predetermined width region. 6. .   6. The image heating apparatus according to claim 1, wherein a width of the predetermined recording material is narrower than a recording material having a maximum width size that can be used.   The image heating apparatus according to claim 1, wherein the heat transfer member is an endless belt.   The image heating apparatus according to claim 1, wherein the nip forming member is a driving rotating body.   A power supply unit, and a control unit that controls power supply from the power supply unit to the heater, and the control unit introduces a recording material having a width larger than a width of the predetermined narrow recording material. In this case, the first heating element is caused to generate heat, and when a recording material having a width equal to or smaller than the predetermined narrow recording material is introduced, the second heating element is caused to generate heat. The image heating apparatus according to claim 1.   The image heating apparatus according to claim 9, wherein the power supply unit is an AC power supply.   A temperature sensor for detecting a heater temperature is provided, and the control unit supplies power to the heater from the power source unit so that the temperature of the heater is maintained at a predetermined temperature based on detected temperature information input from the temperature sensor. The image heating apparatus according to claim 9 or 10, wherein electric power is controlled. A heater, a heat transfer member that moves while sliding in contact with the heater, and a nip forming member that contacts the heater with the heat transfer member interposed therebetween, the heat transfer member and the nip An image heating apparatus that heats an image on a recording material by sandwiching and conveying the recording material at a nip portion formed between the forming member and a substrate short direction of the heater with respect to the recording material conveyance direction in the nip portion The heater used in the image heating apparatus having a pressure force peak on the downstream side of the central part of
An elongated substrate and the substrate are arranged in parallel with a gap between the upstream side and the downstream side with respect to the recording material conveyance direction in the nip portion in the short side direction of the substrate along the longitudinal direction of the substrate. A first heat generating body and a second heat generating body capable of generating heat, the resistance distribution along the length of the first heat generating body is substantially uniform, and the resistance distribution along the length of the second heat generating body Is a resistance distribution in which the resistance of the outer region of the predetermined width region is lower than the resistance of the predetermined width region corresponding to the width of the predetermined recording material.   The heater according to claim 12, wherein the resistance in the predetermined width region and the resistance in the outer region are changed depending on the thickness of the heating element.   The heater according to claim 12, wherein the resistance in the predetermined width region and the resistance in the outer region are changed depending on the material of the heating element.   The heater according to claim 12, wherein the resistance in the predetermined width region and the resistance in the outer region are changed depending on the short width of the heating element.   The heater according to any one of claims 12 to 15, wherein resistance values per unit area of the predetermined width region of the first heating element and the second heating element are substantially the same.   The heater according to any one of claims 12 to 16, wherein a width of the predetermined recording material is narrower than a width of a recording material having a maximum usable width size.