JP2008129501A - Heating element and heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heating element designed such that according to materials to be heated, which are different in size in the lengthwise direction of a substrate, power can be supplied to an area corresponding to the size of the materials to be heated of a heat generation resistor. <P>SOLUTION: The heating element includes the substrate 81a, and the heat generating resistor 81b disposed along the lengthwise direction of the substrate. The heating element is used in a heating device that heats materials S of different sizes. In the heating element, the substrate has electrodes 81d to 81k along the length of the substrate according to the sizes of the materials to be heated, each of the electrodes 81d to 81k being used to supply power to a corresponding area of the heating element, which area corresponds to the size of the material to be heated. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heating body for heating a material to be heated, and a heating apparatus including the heating body, and more particularly, to a heating fixing device (fixing device) mounted on an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer. ) Is suitable.

  As a heat fixing device mounted on an electrophotographic copying machine or printer, a heater having a heating resistor on a ceramic substrate, a flexible member that moves in contact with the heater, and a flexible member Some of them have a heater and a pressure roller that forms a nip portion. Patent Document 1 describes this type of fixing device. The recording material carrying the unfixed toner image is heated while being nipped and conveyed by the nip portion of the fixing device, whereby the toner image on the recording material is heated and fixed to the recording material. This fixing device has an advantage that the time required for starting energization of the heater and raising the temperature to the fixable temperature is short. Therefore, a printer equipped with this fixing device can shorten the time (FPOT: first printout time) until the first image is output after a print command is input. This type of fixing device also has an advantage that power consumption during standby for waiting for a print command is small.

  By the way, when a small-size recording material is continuously printed at the same print interval as a large-size recording material with a printer equipped with a fixing device using a flexible member, the area where the recording material of the heater does not pass (non-sheet passing area) Is known to overheat. If the non-sheet passing region of the heater is excessively heated, the holder for holding the heater and the pressure roller may be damaged by heat.

  Therefore, a printer equipped with a fixing device that forms a fixing nip portion with a heater and a pressure roller via a flexible member, when continuously printing on a small size recording material, when continuously printing on a large size recording material In this way, the control is performed to widen the print interval more, and the excessive temperature rise in the non-sheet passing area of the heater is suppressed.

  However, the control for extending the print interval is to reduce the number of output sheets per unit time, and it is desired to suppress the number of output sheets per unit time to the same level or slightly less than in the case of a large size recording material.

  Therefore, conventionally, the heater of the fixing device has been improved.

  Patent Document 2 describes a heater including a branch electric circuit that is branched from a middle portion along the length of a heat generating resistance layer that generates heat by energization and is selectively energized.

  Patent Document 3 describes a heater configured such that heating resistance layers having different lengths are independently arranged on an insulating substrate and the heating resistance layer can be selectively heated.

  Patent Document 4 describes a heater configured such that a heating resistor layer having different heating regions in the longitudinal direction of a substrate is laminated so that the heating resistor layer can be selectively heated.

Patent Document 5 provides a through hole that penetrates the heating resistor layer in the front and back direction of the insulating substrate and electrically connects the electrode portion formed on the back surface of the insulating substrate and the heating resistor layer. A heater configured to be capable of selectively heating is described.
JP-A-63-313182 Japanese Patent Laid-Open No. 3-144477 JP-A-5-181375 JP-A-6-337605 Japanese Patent Application Laid-Open No. 8-152795

  Patent Documents 2 and 3 tend to increase the width of the insulating substrate as the area for selectively generating heat increases, leading to an increase in the size of the heater, a decrease in thermal efficiency, and an increase in cost.

  In Patent Document 4, the thickness of the insulating substrate is increased, and the heat transfer efficiency is lowered. And there is a tendency to increase the cost because the insulating substrates are stacked.

  In Patent Document 5, there is a possibility that the strength of the insulating substrate is lowered due to the provision of the through hole, and the heater is cracked. As the amount of current flowing through the heat generating resistor layer increases, it becomes necessary to increase the number of through holes and to suppress the amount of current flowing per through hole.

  An object of the present invention is to provide a heating body capable of energizing a region corresponding to the size of the heated material of the heating resistor according to the heated material having different sizes in the longitudinal direction of the substrate, and heating provided with the heated body. To provide an apparatus.

A structure for achieving the above object is a heating body used in a heating device having a substrate and a heating resistor provided along the longitudinal direction of the substrate and heating materials to be heated having different sizes. In
The substrate is provided with a plurality of electrode portions that energize a region of the heating resistor corresponding to the size of the heated material along the longitudinal direction of the substrate according to the size of the heated material. Features.

In addition, a configuration for achieving the above object includes a heating body having a substrate and a heating resistor provided along a longitudinal direction of the substrate, and a flexible member that moves while contacting the heating body. A heating device that includes a heating member and a pressure member that forms a nip portion with the flexible member interposed therebetween, and heats the heated material while sandwiching and conveying the heated material of different sizes in the nip portion. In
The substrate of the heating body is provided with a plurality of electrode portions that energize a region of the heating resistor corresponding to the size of the heated material along the longitudinal direction of the substrate according to the size of the heated material. And a control means for performing control for energizing the electrode portion in the region of the heating resistor corresponding to the size of the material to be heated according to the size of the material to be heated. To do.

  According to the present invention, a heating body capable of energizing a region corresponding to the size of the heated material of the heating resistor according to the heated material having different sizes in the longitudinal direction of the substrate, and heating provided with the heated body Provision of the device can be realized.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

(First embodiment)
(1) Example of image forming apparatus In the following description, with respect to the image forming apparatus, the fixing apparatus, and constituent members of those apparatuses, the longitudinal direction is a direction orthogonal to the recording material conveyance direction on the surface of the recording material. The short side direction is a direction parallel to the recording material conveyance direction on the surface of the recording material. The width is a dimension in a direction parallel to the recording material conveyance direction.

  FIG. 1 is a structural model diagram of an example of an image forming apparatus in which the heating device according to the present invention can be mounted as a heat fixing device (fixing device). This image forming apparatus is an electrophotographic laser beam printer.

  In the image forming apparatus shown in this embodiment, the size of usable recording materials (heated materials) such as recording paper and OHP sheets is A4 size, B5 size, A5 size, and postcard size. These recording materials are set in a feeding unit or a multi-tray. The recording material conveyance reference is a central reference that matches the longitudinal center of the nip portion of the fixing device with the center between the end portions of the recording material along the longitudinal direction of the nip portion.

  In the image forming apparatus of this embodiment, when a print signal (image formation signal) is input from an external device (not shown) such as a host computer, the photosensitive drum 1 as an image carrier is rotationally driven in the direction of the arrow. In the photosensitive drum 1, a photosensitive material such as OPC, amorphous Se, or amorphous Si is formed on a cylindrical substrate such as aluminum or nickel. The outer peripheral surface (surface) of the photosensitive drum 1 is uniformly charged by a charging roller 2 as a charging device. The surface of the photosensitive drum 1 is subjected to scanning exposure by a laser beam L which is ON / OFF controlled according to image information by a laser scanner 3 as an exposure device. As a result, an electrostatic latent image corresponding to the image information is formed on the surface of the photosensitive drum 1. This electrostatic latent image is developed by the developing device 4 using toner (developer), and is visualized as a toner image (developed image). As a developing method, a jumping developing method, a contact developing method, or the like is used, and image exposure and reversal development are often used in combination.

  On the other hand, the recording material S fed one by one from the feeding cassette 5 by the pickup roller 6a is conveyed to the registration roller 6d by the conveyance rollers 6b and 6c. Alternatively, the recording material S fed one by one from the multi-tray 7 by the pickup roller 6e is conveyed to the registration roller 6d. The registration roller 6d conveys the recording material S to the transfer nip portion between the photosensitive drum 1 and the transfer roller 8 as a transfer device in synchronization with the image formation timing. That is, the leading edge of the recording material S is detected by a sensor (not shown) so that the image forming position of the toner image on the surface of the photosensitive drum 1 matches the writing position of the leading edge of the recording material S, and the timing is adjusted. The recording material S is nipped and conveyed by the photosensitive drum 1 and the transfer roller 8 at the transfer nip portion, and the toner image on the surface of the photosensitive drum 1 is electrostatically recorded by the transfer bias applied to the transfer roller 8 in the conveyance process. Transferred onto the S surface.

  The recording material S separated from the surface of the photosensitive drum 1 and exiting the transfer nip portion is introduced into the heat fixing device 9 through the conveyance guide 6f. In the fixing device 9, heat and pressure are applied to the unfixed toner image on the recording material S surface, and the toner image is melted and fixed as a recorded image on the recording material S surface to be fixed.

  After the toner image is fixed, the recording material S is discharged to the discharge tray 10 above the apparatus main body A by the discharge rollers 6g and 6h when the single-sided printing mode is designated. Further, the recording material S after the toner image fixing is switched back by the discharge rollers 6g and 6h when the double-sided printing mode is designated, and is introduced into a reversing path (reversing path) 6i below the apparatus main body A. The recording material S introduced into the reversing path 6i is fed to the registration roller 6d through the transport roller 6c by the transport rollers 6j, 6k, 6l, so that the front and back are reversed. The recording material S is conveyed to the transfer nip portion by the registration roller 6d, and the toner image is transferred to the surface of the recording material S on the photosensitive drum 1 side by the transfer roller 8. The recording material P is introduced into the fixing device 9 and an unfixed toner image is fixed on the surface of the recording material S by heat and pressure, and then discharged to the discharge tray 10 by the discharge rollers 6g and 6h. Reference numeral 11 denotes a foldable discharge tray provided on the left side of the apparatus main body A. The discharge tray 11 is pulled down obliquely upward with respect to the apparatus main body A. Then, the recording material S after fixing the toner image is guided and discharged from the discharge roller 6g to the discharge tray 11 by the flapper 12.

  Residual toner remaining on the surface of the photosensitive drum 1 after separation of the recording material S is removed from the surface of the photosensitive drum 1 by a cleaning device (not shown). The photosensitive drum 1 from which the residual toner has been removed is repeatedly used for image formation.

  The conveying means 6 includes pickup rollers 6a and 6e, conveying rollers 6b, 6c, 6j, 6k, and 6l, a registration roller 6d, a conveying guide 6f, discharge rollers 6g and 6h, a reverse path 6i, and the like.

(2) Heat fixing device 9
FIG. 2 is a schematic cross-sectional view of an example of the fixing device 9. FIG. 3 is a view of the heater unit 21 and the pressure roller 31 as viewed from the recording material introduction side. FIG. 4 is a schematic longitudinal sectional view of the heater unit 21 and the pressure roller 31.

  The fixing device 9 shown in this embodiment includes a heater unit 21 and an elastic pressure roller 31 as a pressure member (backup member). The heater unit 21 includes a fixing film 22 as a flexible member, a heater 23 as a heating body, a heat insulating stay holder 24 as a heating body holding member, and a rigid stay 25 as a reinforcing member.

(A) Fixing film 22
The film 22 is a sleeve-like film member having flexibility and a small heat capacity. In order to enable a quick start, a heat resistant film having a total thickness of 100 μm or less is used as the film 22. As a base layer of the film 22, a heat resistant resin such as polyimide, polyamideimide, PEEK, or a metal member such as SUS, Al, Ni, Ti, Zn having heat resistance and high thermal conductivity is formed alone or in combination. Used. When the material of the base layer is made of resin, high thermal conductive powder such as BN, alumina, Al or the like may be mixed in order to improve thermal conductivity. Moreover, in order to construct the film 22 having a long durability life, a total thickness of 20 μm or more is required as a base layer having sufficient strength and excellent durability. Therefore, the total thickness of the film 22 is optimally 20 μm or more and 100 μm or less.

  Furthermore, in order to prevent toner offset and ensure separation of the recording material S, the surface layer is made of a heat-resistant resin having good releasability such as a fluororesin such as PTFE, PFA, FEP, ETFE, CTFE, PVDF, or a silicone resin. The release layer is coated alone or mixed. The PTFE is polytetrafluoroethylene. PFA is a tetrafluoroethylene perfluoroalkyl vinyl ether copolymer. FEP is a tetrafluoroethylene hexafluoropropylene copolymer. ETFE is an ethylene tetrafluoroethylene copolymer. CTFE is polychlorotrifluoroethylene. PVDF is polyvinylidene fluoride.

  As a coating method, the outer surface of the base layer is etched and then the release layer is dipped, applied by powder spraying, or the surface of the base layer is covered with a tube-shaped one. May be. Or the method of apply | coating the primer layer which is an adhesive agent on the outer surface of a base layer, and coat | covering a release layer may be sufficient.

  Further, a fluorine resin layer or the like having high lubricity may be formed on the inner surface of the film 22 in contact with the heater 23.

(B) Insulated stay holder 24
The stay holder 24 is an elongated member having a substantially bowl-shaped longitudinal section. The stay holder 24 is a member for holding the heater 23 in a concave groove 24a formed on a surface on the nip portion N side, which will be described later, and preventing heat dissipation of the heater 23 in the direction opposite to the nip portion N. The material of the stay holder 24 is a heat resistant resin such as liquid crystal polymer, phenol resin, PPS, PEEK. The film 21 is loosely fitted on the stay holder 24 with a margin.

(C) Rigid stay 25
The stay 25 is an elongated member having a substantially inverted U-shaped longitudinal section. The stay 25 is made of a highly rigid sheet metal such as iron, SUS, or aluminum, and is arranged at the center in the short direction of the stay holder 24.

(D) Elastic pressure roller 30
The pressure roller 30 is a roller member having substantially the same length as the film 21. The pressure roller 30 has an elastic layer 30b formed by foaming heat-resistant rubber such as silicone rubber or fluorine rubber or silicone rubber on the outer periphery of a metal core 30a made of SUS, SUM, Al or the like. A release layer 30c such as PFA, PTFE, FEP or the like is provided on the outer periphery of the elastic layer 30b. The releasable layer 30c is provided as necessary. Both ends of the metal core 30a of the pressure roller 30 are rotatably held by left and right side plates of a device frame (not shown) via bearings 32L and 32R. A heater unit 21 is disposed above the pressure roller 30 in parallel with the pressure roller 30, and both ends of the stay holder 24 are held by the left and right side plates. Then, both ends of the stay holder 24 are pressed against the pressure roller 30 by a pressure spring (pressure means) (not shown). As a result, the pressure roller 30 forms a nip portion (fixing nip portion) N having a predetermined width necessary for heating and fixing the heater 23 and the toner image t with the film 21 interposed therebetween.

(E) Heating heater 23
FIG. 5 is a schematic plan view showing a state in which the protective layer on the back side of the heater 23 is removed. FIG. 6 is an explanatory diagram of an example of a temperature control system for the heater 23.

  The heater 23 has an elongated substrate 81a with high thermal conductivity formed of a ceramic material such as alumina / AlN (aluminum nitride). The substrate 81a is formed wider than the width of the nip portion N.

On the back surface of the substrate 81a, that is, on the surface opposite to the nip portion N side, an energized heating resistor layer 81b as a heating resistor is disposed at one end in the short direction of the substrate 81a (upstream end in the recording material conveyance direction). Are formed along the longitudinal direction of the substrate 81a. The resistance layer 81b is made of, for example, a conductive agent such as Ag / Pd (silver palladium), Ni / Cr, RuO ₂ , Ta ₂ N, TaSiO ₂ and a matrix component such as glass or polyimide. The resistance layer 81b is formed by screen printing, vapor deposition, sputtering, plating, metal foil, or the like by coating it into a linear or narrow strip having a thickness of about 10 μm and a width of about 1 to 5 mm. The length of the resistance layer 81b is set to be the same as the length of the transport area (FIG. 3) of the A4 size recording material S in the nip portion N.

  An insulating protective layer (not shown) such as heat-resistant polyimide, polyamideimide, PEEK, or glass is formed on the resistance layer 81b.

  In addition, on the back surface of the substrate 81a, a plurality of electrode portions 81d, 81e, 81f, and 81g are provided along the longitudinal direction of the substrate 81a on the other end in the short side direction of the substrate 81a (an end portion on the downstream side in the recording material conveyance direction). , 81h, 81i, 81j, 81k. These electrode portions 81d to 81k are all in contact with the resistance layer 81b. The electrode part 81d and the electrode part 81k, the electrode part 81e and the electrode part 81j, the electrode part 81f and the electrode part 81i, and the electrode part 81g and the electrode part 81h are respectively the centers between both ends of the recording material S in the longitudinal direction of the substrate 81a. They are provided symmetrically with respect to the line (center) CL1. This center line CL1 is also the central reference conveyance reference of the recording material S. Accordingly, the length D1 from the electrode portion 81d to the electrode portion 81k is the same as the A4 size recording material length SD1 in the longitudinal direction of the substrate 81a. Further, the length D2 from the electrode part 81e to the electrode part 81j is the same as the recording material length SD2 of B5 size in the longitudinal direction of the substrate 81a. The length D3 from the electrode portion 81f to the electrode portion 81i is the same as the recording material length SD3 of A5 size in the longitudinal direction of the substrate 81a. The length D3 from the electrode portion 81g to the electrode portion 81h is the same as the postcard-sized recording material length SD4 in the longitudinal direction of the substrate 81a. The electrodes 81d, 81e, 81f, 81g, 81h, 81i, 81j, 81k are connected to connectors 81m1, 81m2, 81m3, 81m4, 81m5, 81m6, 81m7, 81m8 as power feeding members, respectively ( FIG. 6).

  On the back surface of the substrate 81a, a temperature detection element 82 such as a thermistor is provided as a temperature detection means at the center in the longitudinal direction of the substrate 81a (FIG. 6). The output signal of the temperature detection element 82 is input to the heater temperature detection circuit (temperature detection means) 41.

  A sliding layer 81c is provided on the surface of the substrate 81a, that is, the surface on the nip portion N side in order to smoothly slide the inner surface of the film 21 with respect to the surface of the substrate 81a with low friction. The sliding layer 81c is formed by coating the above-mentioned fluororesin layers such as PTFE, PFA, FEP, ETFE, CTFE, PVDF, etc. alone or in combination. Alternatively, the sliding layer 81c is formed by thinly applying or vapor-depositing a dry film lubricant made of graphite, molybdenum disulfide, or the like, glass, DLC (diamond-like carbon), or the like. The sliding layer 81c is provided as necessary.

  When the sliding layer 81c is not provided, the surface roughness of the surface of the substrate 81a is suppressed to a predetermined roughness or less, and a lubricant such as a lubricating grease is applied to the surface of the substrate 81a to improve the sliding property with the inner surface of the film 23. The structure which improves thermal efficiency by ensuring and restraining thermal resistance small may be sufficient.

  The heater 23 has the back surface of the substrate 81b facing upward, and the substrate 81b is bonded or pressed against the concave groove 24a of the stay holder 24 by a holding member (not shown). The sliding layer 81 c on the surface of the substrate 81 b of the heater 23 is in contact with the inner surface of the film 22 at the nip portion N.

(3) Heat Fixing Operation of Fixing Device 9 When the image forming apparatus inputs a print signal, the pressure roller 31 of the fixing device 9 is driven by a fixing motor (drive source) M via a drive gear G provided on the core 31a. It is rotated in the direction of the arrow. A rotational force acts on the film 22 by the frictional force between the surface of the pressure roller 31 and the surface of the film 22 due to the rotation of the pressure roller 31. As a result, the inner surface of the film 22 rotates following the outer periphery of the stay holder 24 in the direction of the arrow as the pressure roller 31 rotates while the inner surface of the film 22 is in contact with the sliding layer 81 c of the heater 23.

  Since the film 22 rotates while being in contact with the heater 23 and the stay holder 24, it is necessary to keep the frictional resistance between the heater 23 and the film 22 and between the stay holder 24 and the film 22 small. Therefore, a small amount of lubricant such as heat-resistant grease is interposed on the surface of the heater 23 that contacts the film 22 and the surface of the stay holder 9. Thereby, the film 22 can be smoothly rotated.

  When the print signal is input, the microprocessor (control means) 43 takes in the detection signal of the recording material S detected by the recording material size detection circuit (size detection means) 42 and, based on the detection signal, the recording material S. Determine the size of the. Then, according to the size of the recording material S, control for energizing the electrode portion in the region of the resistance layer 81a corresponding to the recording material S is performed. That is, an electrode portion corresponding to the size of the recording material S is selected from a plurality of electrode portions from the electrode portions 81d to 81k, and the power supply circuit (power supply means) 44 is controlled so as to energize the selected electrode portion. To do. The power feeding circuit 44 includes a power feeding unit 44a having a power source (not shown), a first switch S1, a second switch S1, and the like. The first switch S1 includes a movable contact connected to the power supply unit 44a and fixed contacts of the connectors 81m1 to 81m4 connected to the electrode units 81d to 81g, respectively. The second switch S2 includes a movable contact connected to the power supply unit 44a and fixed contacts of the connector 81m5 to the connector 81m8 connected to the electrode unit 81h to the electrode unit 81k, respectively.

  When the microprocessor 43 determines that the size of the recording material S is A4 size, the microprocessor 43 switches the switches S1, S1 and S2 so as to connect the movable contacts of the first and second switches S1, S2 to the fixed contacts of the connectors 81m1, 81m8. S2 is controlled. As a result, the electrode portions 81d and 81k are energized from the power feeding circuit 44, and the resistance layer 81b generates heat in the entire area between the electrode portions 81d and 81k (energization area D1).

  When the microprocessor 43 determines that the size of the recording material S is B5 size, the microprocessor 43 switches the switches S1, S1 and S2 to connect the movable contacts of the first and second switches S1, S2 to the fixed contacts of the connectors 81m2, 81m7. S2 is controlled. As a result, the electrode portions 81e and 81j are energized from the power feeding circuit 44, and the resistance layer 81b quickly generates heat in the entire area between the electrode portions 81e and 81j (energization area D2).

  When the microprocessor 43 determines that the size of the recording material S is A5 size, the microprocessor 43 switches the switches S1, S1 and S2 to connect the movable contacts of the first and second switches S1, S2 to the fixed contacts of the connectors 81m3, 81m6. S2 is controlled. As a result, the electrode portions 81f and 81i are energized from the power supply circuit 44, and the resistance layer 81b quickly generates heat in the entire area between the electrode portions 81f and 81i (energization area D3).

  When the microprocessor 43 determines that the size of the recording material S is a postcard size, the microprocessor 43 switches the switches S1, S1 and S2 to connect the movable contacts of the first and second switches S1, S2 to the fixed contacts of the connectors 81m4, 81m5. S2 is controlled. As a result, the electrode portions 81g and 81h are energized from the power feeding circuit 44, and the resistance layer 81b quickly generates heat in the entire area between the electrode portions 81g and 81h (energization area D4).

  As the resistance layer 81b generates heat according to the size of the recording material S, the heater 23 quickly rises in temperature. The temperature rise of the heater 23 is detected by the temperature detection element 82. The output signal of the temperature detection element 82 is input to the heater temperature detection circuit 41, and the microprocessor 43 takes in the temperature detection signal from the heater temperature detection circuit 41. Based on the temperature detection signal, the microprocessor 43 sets the voltage duty ratio and wave number so that the temperature of the heater 23 becomes the optimum fixing temperature (target temperature) for fixing the unfixed toner image t to the recording material S. Etc. are appropriately controlled to adjust the heater 23 temperature. That is, the energization to the resistance layer 81b is controlled so that the detected temperature of the temperature detecting element 82 maintains the target temperature.

  In the heater 23 temperature adjustment state, the recording material S having a size corresponding to the heat generation area (energization area) of the resistance layer 81 b is introduced into the nip portion N, and the recording material S is nipped and conveyed by the nip portion N. In the conveying process, the pressure of the nip portion N is applied to the unfixed toner image t on the surface of the recording material S and the heat of the heater 23 is applied through the film 22, whereby the unfixed toner image t Is melt-fixed on the recording material S surface. The recording material S exiting the nip portion N is separated from the surface of the film 22 by the curvature, and is conveyed to the discharge roller 6g (FIG. 1).

  As the recording material size detection circuit 42, a sensor provided in the conveyance path of the recording material S so that the recording material S of a predetermined size can be detected in the conveyance path of the recording material S is used. A recording material size signal instructed from an external device together with the print signal may be used as the detection signal S1 of the recording material S. In that case, the recording material size detection circuit 42 can be omitted, and the configuration of the image forming apparatus can be simplified.

(4) Experimental Example An experimental example performed to confirm the effect of the fixing device 9 of this embodiment will be described.

  The configuration details of the individual components of the fixing device 9 used in the experiment of this embodiment are as follows.

  First, as a basic configuration, the heater 23 is a high thermal conductive AlN substrate having a width of 10 mm as the substrate 81a. On the back surface of the AlN substrate, a resistive layer 81b is screen-printed as a paste obtained by mixing a mixture of Ag / Pd conductive agent and phosphate glass as a matrix component with an organic solvent, a binder, a dispersant and the like. And baked at 600 ° C. The resistance layer 81b was formed over a length of 210 mm as shown in FIG.

  In the AlN substrate 81a, in order to apply a voltage to the resistance layer 81b, a plurality of electrode portions 81d to 81k provided on the same surface side as the resistance layer 81b are also formed by screen printing using an Ag / Pd-based conductive paste. The The electrode portions 81d to 81k have a Pd content ratio significantly lower than that of the resistance layer 81b and do not generate heat. The resistance layer 81b is covered with a glassy protective layer (not shown).

  Further, a phosphoric acid-based glass having a thickness of 10 μm was formed as a sliding layer 81c on the surface of the AlN substrate 81a by screen printing.

  The film 22 was formed into a cylindrical shape having an outer diameter of 24.13 mm by applying a primer layer of 5 μm and a PFA resin by 10 μm dipping to a cylindrical seamless polyimide having an inner diameter of 24 mm and a thickness of 50 μm.

  The pressure roller 31 was formed by forming a silicone rubber layer with a thickness of 4 mm on an Al cored bar of 22 mm, and covering the outer layer with a PFA tube.

  Further, the image forming apparatus equipped with the fixing device 9 can print 25 sheets per minute at a process speed of 150 mm / sec.

  The resistance value of the resistance layer 81b of the heater 23 is 12.5Ω, and the power when operated at a voltage of 100V is 800W. This is the state of 100% energization, and this is energized as 0, 2.5, 5, 7.5, 10,..., 95, 97.5, 100% every 2.5% by known phase control. The electric power supplied to the heater 23 is controlled by controlling the duty (duty).

  In this embodiment, the temperature controlled by the temperature detecting element 82 on the back surface of the heater 23 for fixing the toner to the recording material S is set to 200 ° C. The fixing device 9 is started up from the room temperature so as to reach 200 ° C. When starting up the fixing device 9, the resistance layer 81 b is energized without the recording material S in the fixing device 9.

  In any of the energization areas D1 to D4 of the resistance layer 81b, it took about 7 to 8 seconds in time for the temperature detected by the temperature detection element 82 to reach 200 ° C.

  Therefore, in the fixing device 9 of this embodiment, the fixing device 9 is always started up and the fixing operation can be started in 8 seconds. Actually, the recording material S is entered at the timing when the recording material S enters the nip N at this moment. To feed.

  When the size determined by the recording material size detection circuit 42 is A4 size, energization is performed between the electrode portion 81d and the electrode portion 81k (energization area D1) for fixing. Similarly, when the recording material size is B5, A5, or a postcard, a predetermined electrode portion is selected and fixing is performed by changing the energization area (length).

  Since the lengths of the energization areas D2 to D4 are shorter than the energization area D1, the resistance value between the energization areas is lowered by the ratio. Therefore, in order to align the heat generation amount per unit length, each initial input voltage was set as follows.

  Here, the initial input voltage value in the energization areas D2 to D4 was obtained by the following formula because it is based on 100 V as the initial input voltage when the energization area is D1.

Initial input voltage value (V) = 100 × √ (resistance layer length / A4 resistance layer length)
However, when the fixing device 9 is started up from the room temperature state, the initial input voltage value obtained by the above formula is energized with the value being 100%. As described above, the energization duty (duty) is appropriately controlled by the phase control.

  Using the above apparatus, a paper passing test and a fixing device temperature measurement were performed.

Experiment (1): Alternate printing of postcards and A4 size paper One postcard and one A4 size plain paper are printed alternately and continuously. A postcard and A4 paper were printed at a speed of 25 sheets per minute. Postcards with a basis weight of 186 g / m ² were used, and A4 paper was office planner paper (A4 64 g / m ² ) manufactured by Canon Marketing Japan. A paper passing experiment was performed with the image forming apparatus of this example and the conventional image forming apparatus, and Table 2 shows the results.

  Here, in the fixing device mounted on the conventional image forming apparatus, the heater 91 has only two electrode portions 81b (81n, 81o) at the longitudinal ends of the back surface of the AlN substrate 81a as shown in FIG. In addition, a configuration in which the energization area is always D1 was used. The other configuration is the same as that of the first embodiment.

  As shown in Table 2, in the image forming apparatus of the present embodiment, no particular problem occurred even when the postcard and the A4 paper were continuously printed alternately. FIG. 8 shows a postcard energization area D4 and an A4 paper energization area D1 in the heater 23. As described above, when fixing the postcard, since the energizing area of the heater 23 is controlled by setting the postcard size (D4 = 100 mm), no heat is generated in the non-sheet passing areas on both sides of the energizing area D4. This is because the temperature of the paper passing area does not rise abnormally (FIG. 8).

  On the other hand, in the comparative conventional example, hot offset has occurred on both sides of the A4 paper from the 34th sheet. FIG. 9 shows a postcard energization area D4 and an A4 paper energization area D1 in the heater 91. In the conventional example, since the entire resistance layer 81b is used even for fixing a postcard, the temperature of the non-sheet passing area on both sides of the energizing area D4 rises during postcard fixing, and when fixing A4 paper, the position is indicated by Ns. A hot offset has occurred.

Experiment (2) Temperature measurement during continuous postcard feeding Experiment (1) showed that the heater 23 of this example had an effect that no image defect occurred. Immediately after heating the heater 23 to verify the reason, FIG. 10 shows the results of measurement using a non-contact thermometer for the film 22 temperature. The graph shown in FIG. 10 is the temperature of the tenth sheet when ten postcards are printed continuously.

  In this embodiment, since the energization area is narrowed to a postcard size (D4 = 100 mm), the area outside the postcard paper feeding area is not heated. On the other hand, in the comparative conventional example, the temperature was increased until it reached 250 ° C. in the outer area of the postcard paper passing area. In both cases, the postcard passing area was controlled to a control temperature of 200 ° C.

  As described above, by using the heater 23 of this embodiment, the electrode portions 81d to 81k corresponding to the size of the recording material S can be energized according to the size of the recording material S. For this reason, even if a small size recording material S is continuously printed at the same print interval as the large size recording material S, the temperature rise in the non-sheet passing area can be suppressed.

  In the present embodiment, the paper passing experiment for the postcard size has been described, but it goes without saying that the effects of the present embodiment are also obtained for the B5 size and the A5 size.

  According to the heater 23 of the present embodiment, it is possible to increase the types of energization areas simply by increasing the number of electrode portions 81d to 81k without increasing the width of the substrate 81a (width in the recording material conveyance direction).

  Further, by arranging the resistance layer 81b and the electrode portions 81d to 81k on the surface opposite to the nip portion N of the substrate 81a, it is not necessary to use means such as a through hole, in other words, there is no decrease in mechanical strength, It is possible to increase the types of energization areas.

  In addition, since it is possible to increase the types of energization areas without laminating a resistance layer on the substrate 81a, it is possible to save power without a decrease in heat transfer efficiency.

  Further, since the resistance layer 81b can be heated by a required recording material length corresponding to the recording material length of the recording material S, not only the hot offset is prevented, but also when fixing a narrow paper. It was possible to save power by not heating the necessary parts.

  Further, since the heat generation amount per unit length of the resistance layer 81d is aligned, the power consumption is determined by the ratio of the length of the resistance layer 81d. Therefore, when the energizing area is set to a postcard size (D4 = 100 mm) by fixing paper with a short recording material length, there is an effect that the power can be reduced by about 0.5 times (100/210).

  Further, it is possible to appropriately control the energization area as appropriate in order to avoid the non-sheet passing area of the film 22 and the pressure roller 31 from being cooled following the large number of postcards fixed.

  Further, if the temperature difference between the film 22 and the pressure roller 31 is excessively large in the longitudinal direction, there is a concern that paper wrinkles may occur due to a difference in thermal expansion. Therefore, it is effective to select an energized area as appropriate.

(Second embodiment)
Another example of the heater will be described. In the present embodiment, members / portions common to the first embodiment are denoted by the same reference numerals, and descriptions of the members / portions are incorporated. The same applies to Example 3 and Example 4.

  FIG. 11 is an explanatory diagram of the heater 23 of the present embodiment, and is a plan model diagram in a state where the protective layer on the back surface side of the heater 23 is removed.

  In the heater 23 shown in this embodiment, a resistance layer 81b is provided on one end side and the other end side in the short direction perpendicular to the longitudinal direction of the substrate 81a. The plurality of electrode portions 81d to 81k are provided on the same surface as the surface of the substrate 81a on which the resistance layer 81b is provided, and are provided in the center in the short direction.

  In the heater 23 of this embodiment, the two resistance layers 81b provided on one end side and the other end side in the short direction of the substrate 81a are symmetrical with respect to the center line CL2 in the short direction of the substrate 81a. The resistance values of the two resistance layers 81b were each set to 25Ω so that the heat generation amount was the same as in the first embodiment. Between the two resistance layers 81b, electrode part 81d and electrode part 81k, electrode part 81e and electrode part 81j, electrode part 81f and electrode part 81i, electrode part 81g and electrode part 81h, respectively, center line CL1 Arranged symmetrically with respect to the reference.

  Also in this example, when the two experiments of Experiment (1) and Experiment (2) described in Example 1 were performed, the same effect could be confirmed. This is because although the arrangement of the resistance layer 81b is different, the energization area in the longitudinal direction is the same as that of the first embodiment, and thus the same effect is obtained.

  Further, the configuration in which the resistance layers 81b are arranged symmetrically with respect to the center line CL2 on one end side and the other end side in the short direction of the substrate 81a, which is a feature of the present embodiment, is the temperature of the heater 8 in the recording material conveyance direction. Distribution is almost symmetrical. Therefore, there is an advantage that the thermal stress is reduced and the heater 23 is hardly damaged.

  In order to confirm the effect of the heater 23 of the present embodiment, the temperature distribution in the recording material conveyance direction (see FIG. 12) on the back surface of the heater 23 was measured for the heater 23 of the present embodiment and the heater 23 of the first embodiment. FIG. 13 shows the measurement results.

  The above measurement is a state after 3 sec when 800 W is energized in the area D1 from the electrode part 81d to the electrode part 81k in the resistance layer 81b using a single heater 23.

  As can be seen from FIG. 13, in the heater 23 of this embodiment, the two resistance layers 81b are arranged symmetrically with respect to the center line CL2 in the short direction of the substrate 81a. It is almost symmetrical. In contrast, in the heater 23 of Example 1, the resistance layer 81b is disposed at one end in the short direction of the substrate 81a, and therefore the temperature distribution is not symmetric at the upstream end in the recording material conveyance direction. .

  Also in the heater 23 of the first embodiment, when the heater 23 is sufficiently heated so as to reach the fixing temperature, the substrate 81a has a high thermal conductivity, so that a substantially symmetrical temperature distribution is obtained. However, when the heater 23 of the first embodiment is not a single heater 23 but is incorporated as a heat source of the fixing device 9, it takes time to reach a sufficiently heated equilibrium state for supplying heat to other components. End up.

  This asymmetric state of the temperature distribution acts on the substrate 81a as thermal stress, and if the mechanical strength of the substrate 81a cannot withstand this, it will break down, so it is preferable to keep the thermal stress low.

  In this embodiment, the resistance layer 81b is arranged symmetrically with respect to the center line CL2 in the short direction of the substrate 81a on the high thermal conductive substrate 81a, so that the heater 23 resistant to thermal stress can be used in the embodiment. The effect similar to 1 was able to be acquired.

(Third embodiment)
Another example of the heater 23 will be described.

  The heater 23 shown in the present embodiment is the same as the heater 23 of the second embodiment, and the two resistance layers 81b correspond to the electrode portions 81d to 81k in the width corresponding to the electrode portions 81d to 81k in the short direction of the substrate 81a. It is characterized in that it is narrower than the width of the region that is not. Accordingly, it is possible to provide the heater 23 in which the heat generation amount of the resistance layer 81b in the vicinity of the electrode portions 81d to 81k is increased with respect to the heat generation amount of the portion where the electrode portions 81d to 81k are not disposed.

  By using the heater 23 of the present embodiment, it is possible to improve that the heat escapes to the connectors 81m1 to 81m8 brought into contact with the electrode portions 81d to 81k, and the fixing property is rarely deteriorated at that portion.

  FIG. 14 is an explanatory diagram of the heater 23 of the present embodiment, and is a plan model diagram in a state where the protective layer on the back side of the heater 23 is removed.

  In this example, regarding the resistance value per unit length in the longitudinal direction of the resistance layer 81b, the portions near the electrode portions 81d to 81k are increased by 3% with respect to the resistance values of portions not near the electrode portions 81d to 81k. . The portions where the width of the resistance layer 81b is narrowed are +0.5 mm in the recording material conveyance direction with respect to the electrode portions 81d to 81k.

  In the heater 23 of this example, the resistance values of the two resistance layers 81b are each 25Ω, as in Example 2, so that the heating value is the same as in Examples 1 and 2. The rest of the configuration was the same as in Example 1.

  Also in this example, when the two experiments of Experiment (1) and Experiment (2) described in Example 1 were performed, the same effect could be confirmed.

  Further, the deterioration of the fixing property at the positions of the electrode portions 81d to 81k was suppressed, and there was no problem.

(Fourth embodiment)
Another example of the heater 23 will be described.

  The heater 23 shown in this embodiment is characterized in that a plurality of electrode portions 81d to 81k are provided on the resistance layer 81b along the longitudinal direction of the substrate 81a.

  FIG. 15 is an explanatory diagram of the heater 23 of the present embodiment, and is a plan model diagram in a state where the protective layer on the back surface side of the heater 23 is removed.

  In the case of the heater 23 of FIG. 5 of the first embodiment, even if a plurality of electrode portions 81d to 81k are provided along the longitudinal direction of the substrate 81a, the width in the recording material conveyance direction does not increase according to the number of electrode portions. The widths of the electrode portions 81d to 81k and the width of the resistance layer 81b are necessarily required. This means that the width of the substrate 81a cannot be further reduced, that is, the limit of downsizing of the fixing device 9 occurs.

  Further, in the case of the heater 23 of FIGS. 11 and 14 shown in the second and third embodiments, the resistance layer 81b is disposed on one end side and the other end side in the short direction of the substrate 81a. Therefore, there is no heat generation at the longitudinal center of the substrate 81a between the two resistance layers 81b, and the capability as the heater 23 is not fully exhibited.

  Therefore, in this embodiment, a plurality of electrode portions 81d to 81k are provided on the resistance layer 81b in the longitudinal direction of the substrate 81a, thereby reducing the width of the substrate 81a of the heater 23 as much as possible and increasing the capability of the heater 23. .

  The width of the substrate 81a was 7 mm. The rest of the configuration was the same as in Example 1.

  Also in this example, when the two experiments of Experiment (1) and Experiment (2) described in Example 1 were performed, the same effect could be confirmed.

[Other]
The electrode portions 81d to 81k of the heater 32 are also used in the case of one-side reference for transporting the recording material S having a different size with reference to one of the one end and the other end of the recording material in the longitudinal direction of the substrate 81a. The recording material S is provided symmetrically with respect to the center line CL1. When the one end portion of the recording material is used as a reference, the electrode portion 81d on the one end portion side serves as a common electrode portion for recording materials having different sizes, so that the electrode portions 81e to 81g can be omitted. When the other end portion of the recording material is used as a reference, the electrode portion 81k on the other end side serves as a common electrode portion for recording materials having different sizes, so that the electrode portions 81h to 81j can be omitted.

1 is a configuration model diagram of an example of an image forming apparatus. FIG. 3 is a cross-sectional model diagram of an example of a fixing device. The figure which looked at the heater unit and the pressure roller from the introduction side of the recording material. The longitudinal cross-sectional model figure of a heater unit and a pressure roller. FIG. 3 is a diagram illustrating an example of a heater according to the first embodiment. Explanatory drawing of an example of the temperature control system of a heater. The figure showing the structure of the heater of a comparative prior art example. The figure showing the energization area of the postcard in the heater which concerns on Example 1, and the energization area of A4 paper. The figure showing the energizing area of the postcard and the energizing area of A4 paper in the heater according to the comparative conventional example. The figure showing the film temperature immediately after the heating of the heater which concerns on Example 1, and the film temperature immediately after the heating of the heater which concerns on a comparative conventional example about each of a postcard and A4 size paper. FIG. 6 is a diagram illustrating an example of a heater according to a second embodiment. FIG. 6 is a diagram illustrating a recording material conveyance direction in which a temperature distribution on the back surface of the heater is measured for the heater according to the second embodiment and the heater according to the first embodiment. The figure showing the measurement of the temperature distribution of the heater back surface for the heater according to the second embodiment and the heater according to the first embodiment. FIG. 6 is a diagram illustrating an example of a heater according to a third embodiment. FIG. 6 is a diagram illustrating an example of a heater according to a fourth embodiment.

Explanation of symbols

22: fixing film, 23: heater, 81a: substrate, 81b: energization heating resistance layer, 81d to 81k: electrode portion, 31: pressure roller, S: recording material

Claims (13)

In a heating element used in a heating device having a substrate and a heating resistor provided along the longitudinal direction of the substrate, and heating a material to be heated having a different size,
The substrate is provided with a plurality of electrode portions that energize a region of the heating resistor corresponding to the size of the heated material along the longitudinal direction of the substrate, depending on the size of the heated material. Characteristic heating element.   The heating resistor is provided on one end side in the short direction perpendicular to the longitudinal direction of the substrate, and the plurality of electrode portions are short in the same plane as the surface of the substrate on which the heating resistor is provided. The heating element according to claim 1, wherein the heating element is provided on the other end side of the heating element.   The heating resistor is provided on one end side and the other end side in the short direction perpendicular to the longitudinal direction of the substrate, and the plurality of electrode portions are flush with the surface of the substrate on which the heating resistor is provided. The heating body according to claim 1, wherein the heating body is provided at the center in the lateral direction.   4. The heat generating resistor according to claim 3, wherein a width of a region corresponding to the electrode portion is narrower than a width of a region not corresponding to the electrode portion in a short direction perpendicular to the longitudinal direction of the substrate. Heating body.   The heating body according to claim 1, wherein the plurality of electrode portions are provided on the heating resistor over the longitudinal direction of the substrate.   6. The heating according to claim 1, wherein the plurality of electrode portions are provided symmetrically with respect to a center between both end portions of the heated material in a longitudinal direction of the substrate. body. A heating body having a substrate and a heating resistor provided along the longitudinal direction of the substrate, a flexible member that moves while contacting the heating body, and the heating body sandwiching the flexible member And a pressure member that forms a nip portion, and a heating device that heats the heated material while sandwiching and conveying the heated material having different sizes in the nip portion,
The substrate of the heating body is provided with a plurality of electrode portions that energize a region of the heating resistor corresponding to the size of the heated material along the longitudinal direction of the substrate according to the size of the heated material. And a control means for performing control for energizing the electrode portion in the region of the heating resistor corresponding to the size of the material to be heated according to the size of the material to be heated. Heating device.   The heating resistor is provided on one end side in the short direction perpendicular to the longitudinal direction of the substrate, and the plurality of electrode portions are short in the same plane as the surface of the substrate on which the heating resistor is provided. The heating device according to claim 7, wherein the heating device is provided on the other end side of the heating device.   The heating resistor is provided on one end side and the other end side in the short direction perpendicular to the longitudinal direction of the substrate, and the plurality of electrode portions are flush with the surface of the substrate on which the heating resistor is provided. The heating device according to claim 7, wherein the heating device is provided at the center in the short direction.   8. The heating resistor according to claim 7, wherein a width of a region corresponding to the electrode portion is narrower than a width of a region not corresponding to the electrode portion in a short direction perpendicular to the longitudinal direction of the substrate. Heating device.   The heating according to any one of claims 7 to 10, wherein the plurality of electrode portions are provided symmetrically with respect to a center between both end portions of the material to be heated in a longitudinal direction of the substrate. apparatus.   The heating device according to claim 7, wherein the plurality of electrode portions are provided on the heating resistor over the longitudinal direction of the substrate.   The heating according to any one of claims 7 to 12, wherein the heating resistor and the plurality of electrode portions are provided on a surface of the substrate opposite to the surface on the flexible member side. apparatus.