JP2009139460A - Heating member and image heating apparatus provided with the heating member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce excessive rising of temperature in a region where a recording material is not passed in a heat generating region, and to suppress rising of the temperature around an electrode section of a heat generating substrate. <P>SOLUTION: A heating member is used for an image heating apparatus for heating the image carried on the recording material. The heating member 22 is provided with: a long heat generating substrate 22a for generating heat by being energized; and electrode sections 22d and 22e which are provided on the heat generating substrate in an end section in the longer direction of the heat generating substrate and which supplies power to the heat generating substrate, wherein conductive sections 22f and 22g which are electrically connected with the electrode section and extended from the electrode section to the center in the longitudinal direction of the heat generating substrate, is provided on the heat generating substrate, a heat generating region H2 is provided in a region which is on the side of the center in the longitudinal direction of the heat generating substrate from the conducting section. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a heating member suitable for use in a heat fixing device (fixing device) mounted on an image forming apparatus such as an electrophotographic copying machine or an electrophotographic printer, and an image heating device using the heating member.

  As an image heating device (fixing device) mounted on an electrophotographic printer or copying machine, a heater having a heating resistor on a ceramic substrate, a flexible member that moves while contacting the heater, a flexible member Some of them have a pressure roller that forms a nip portion with the heater via the. 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 on the recording material. This fixing device has an advantage that it takes a short time to start energizing the heater and raise the temperature to a fixable temperature. Therefore, a printer equipped with this fixing device can shorten the time (FPOT: First Print Out Time) from when a print command is input until the first image is output. This type of fixing device also has an advantage that power consumption during standby waiting for a print command is small.

  By the way, when a small-sized recording material is continuously printed at the same print interval as a large-sized 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 area of the heater is excessively heated, the holder and the pressure roller that hold the heater may be damaged by heat.

  Therefore, a printer equipped with a fixing device using a flexible member has a control for widening the print interval when continuously printing on a small size recording material, compared with the case of continuously printing on a large size recording material. The excessive temperature rise in the paper passing area is suppressed.

  However, the control for extending the print interval is to reduce the number of output sheets per unit time, and it is desirable 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.

  In view of this, it has been considered to use a heater (NTC = Negative Temperature Coefficient) whose resistance value decreases as the temperature rises as the heater used in the above-described fixing device.

  Patent Document 2 discloses a method in which a semicircular rod member mainly composed of silicon carbide (SiC) is used as an energization heating element, and a power supply electrode of a metal molded body is attached to both ends in the longitudinal direction of this member. ing. This uses the negative resistance temperature characteristic (NTC characteristic) of silicon carbide in the temperature range from room temperature to about 800 ° C., and suppresses the non-sheet-passing portion temperature rise in which the non-sheet-passing region overheats. .

Patent Document 3 discloses a method of embedding a carbon-based heating element as an energization heating element in an aluminum nitride substrate and providing power supply electrodes at both ends of the carbon-based heating element. This also uses the negative resistance temperature characteristic (NTC characteristic) of the carbon-based heating element to suppress the temperature increase in the non-sheet passing portion where the temperature increases in the non-sheet passing region.
JP-A-63-313182 JP 06-019347 A JP 2006-134746 A

  The present invention is a further development of the above prior art. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a heating member capable of reducing an excessive temperature rise in an area where the recording material in the heat generating area does not pass and suppressing a temperature rise around the electrode portion of the heat generating substrate, and an image using the heating member. It is to provide a heating device.

  A configuration for achieving the above object is a heating member used in an image heating apparatus that heats an image carried on a recording material, and includes an elongated heating substrate that generates heat when energized, and a longitudinal end portion of the heating substrate In the heating member having an electrode portion provided on the heat generating substrate for supplying power to the heat generating substrate, the heating member is electrically connected to the electrode portion so as to go from the electrode portion toward the longitudinal center of the heat generating substrate. An extended conductive portion is provided on the heat generating substrate, and a heat generating region is provided in a region on the longitudinal center side of the heat generating substrate from the conductive portion.

  Further, a configuration for achieving the above object is a heating having an elongated heat generating substrate that generates heat by energization and an electrode portion that is provided on the heat generating substrate at a longitudinal end portion of the heat generating substrate and supplies power to the heat generating substrate. An image heating apparatus having a member and a flexible member that moves while being in contact with the heating member, and heats an image carried on the recording material via the flexible member by heat generated by the heat generating substrate The heating member has a conductive portion on the heat generating substrate that is electrically connected to the electrode portion and extends from the electrode portion toward the longitudinal center of the heat generating substrate, and the heating member generates the heat from the conductive portion. A heat generating region is provided in a region on the center side in the longitudinal direction of the substrate.

  According to the present invention, a heating member that can reduce an excessive temperature rise in an area where the recording material of the heat generation area does not pass and can suppress a temperature rise around the electrode portion of the heat generation substrate, and an image heating apparatus using the heating member Can provide.

  The present invention will be described with reference to the drawings.

[Example]
(1) Image Forming Apparatus Example FIG. 1 is a schematic configuration model diagram of an example of an image forming apparatus in which the image heating apparatus according to the present invention can be mounted as a heat fixing apparatus. This image forming apparatus is an electrophotographic laser beam printer.

  The printer shown in this embodiment has a rotating drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) 1 as an image carrier. The photosensitive drum 1 has a configuration in which a photosensitive material layer such as OPC, amorphous Se, or amorphous Si is formed on the outer peripheral surface of a cylinder (drum) -like conductive substrate such as aluminum or nickel.

  The photosensitive drum 1 is rotationally driven in the clockwise direction indicated by an arrow a at a predetermined peripheral speed (process speed). In the rotation process, the outer peripheral surface (surface) of the photosensitive drum 1 has a predetermined polarity by a charging roller 2 as a charging unit.・ Evenly charged to the potential. Scanning exposure L is performed with a laser beam modulated and controlled (ON / OFF control) according to image information output from the laser beam scanner 3 to the uniformly charged surface of the photosensitive drum 1 surface. As a result, an electrostatic latent image corresponding to the target image information is formed on the surface of the photosensitive drum 1.

  The latent image is developed and visualized by using the toner t by the developing device 4 as developing means. As a development method, a jumping development method, a two-component development method, a FEED development method, or the like is used, and is often used in combination with image exposure and reversal development.

  On the other hand, the recording material P stacked and stored in the feeding cassette 9 is driven one by one by driving the feeding roller 8 and conveyed to the registration roller 11 through a sheet path having the guide 10 and the registration roller 11. The registration roller 11 feeds the recording material P to the transfer nip T between the surface of the photosensitive drum 1 and the outer peripheral surface (surface) of the transfer roller 5 at a predetermined control timing. The recording material P is nipped and conveyed by the transfer nip portion TN, and the toner image on the surface of the photosensitive drum 1 is sequentially transferred onto the surface of the recording material P by a transfer bias applied to the transfer roller 5 in the conveyance process. As a result, the recording material P carries an unfixed toner image.

  The recording material P carrying the unfixed toner image is sequentially separated from the surface of the photosensitive drum 1, discharged from the transfer nip T, and introduced into the nip N of the heat fixing device 6 through the conveyance guide 12. The recording material P is heated and fixed on the surface of the recording material P by receiving heat and pressure from the nip portion N of the fixing device 6.

  The recording material P that has exited the fixing device 6 passes through a sheet path having a conveying roller 13, a guide 14, and a paper discharge roller 15, and is printed out on a paper discharge tray 16.

  Further, the surface of the photosensitive drum 1 after separation of the recording material is cleaned by a cleaning device 7 as a cleaning means to remove adhered contaminants such as transfer residual toner, and is repeatedly used for image formation.

  The above is the image forming operation (printing operation) of the printer of this embodiment.

  The feeding cassette 9 has a movable regulation guide (not shown) for loading and storing various types of recording materials P of different sizes in the feeding cassette 9, and the regulation guide is used according to the size of the recording material P. The recording material P is displaced and stored in the feeding cassette 5. Accordingly, various types of recording materials P having different sizes can be sent out from the feeding cassette 9 on the basis of the central conveyance reference. Here, the central conveyance reference refers to a conveyance mode in which the recording material P is conveyed on the basis of the approximate center between the end surfaces in the width direction orthogonal to the conveyance direction of the recording material P on the surface of the recording material P.

  The printer of this embodiment is a printer compatible with A4 portrait and LTR portrait paper, and the print speed is 50 sheets / minute.

(2) Fixing device 6
In the following description, regarding the fixing device and the members constituting the fixing device, 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 the short direction. Regarding the recording material, the width direction is a direction orthogonal to the recording material conveyance direction on the surface of the recording material. The width direction is also the longitudinal direction of the fixing device and the members constituting the fixing device. The longitudinal width is a dimension in the width direction of the recording material.

  FIG. 2 is a cross-sectional configuration model diagram of an example of the fixing device 6. FIG. 3 is a vertical cross-sectional configuration model diagram of the fixing device 6. FIG. 4 is a view of the fixing device 6 as viewed from the recording material introduction side. The fixing device 6 is a film heating type fixing device.

  Reference numeral 21 denotes a horizontally long film guide member (stay) extending in the longitudinal direction. The film guide member 21 is formed in a saddle shape having a substantially semicircular cross section. Reference numeral 22 denotes a horizontally long heating member (hereinafter referred to as a heating body) accommodated and held in a groove 21a provided along the longitudinal direction at the center in the short direction of the lower surface of the film guide member 21. Reference numeral 23 denotes a horizontally long flexible member (flexible sleeve) extending in the longitudinal direction. The flexible member 23 is an endless belt-like (cylindrical) heat-resistant film (hereinafter referred to as a film) that is loosely fitted on the film guide member 21 that holds the heating body 22.

  Reference numeral 24 denotes an elastic pressure roller (hereinafter referred to as a pressure roller) as a pressure member extending along the longitudinal direction. The pressure roller 24 includes a metal core 24a, an elastic layer 24b provided on the outer periphery of the metal core 24a, a release layer 24c provided on the outer periphery of the elastic layer 24b, and the like. The pressure roller 24 is pressed against the surface protective layer 22 h of the heating body 22 with the film 23 interposed therebetween. Pressurization of the heating roller 22 by the pressure roller 24 is performed using a pressure means (not shown) such as a pressure spring. The pressure roller 24 elastically deforms the elastic layer 24b by the pressure applied by the pressure means, thereby providing a predetermined width between the outer peripheral surface (surface) of the pressure roller 24 and the outer peripheral surface (surface) of the film 23. Nip portion (fixing nip portion) N is formed. The pressure roller 24 is counterclockwise indicated by an arrow b at a predetermined peripheral speed (process speed) when a driving gear G provided at the longitudinal end of the cored bar 24a is rotated by a driving source M such as a motor. Rotated in the direction.

  The film guide member 21 is a molded product of a heat resistant resin such as PPS (polyphenylene sulfite) or LCP (liquid crystal polymer).

  The heating element 22 is a heater having a low heat capacity as a whole mainly composed of a ceramic resistance heating element whose resistance is adjusted so that the substrate itself generates heat when energized. As shown in FIGS. 5A and 5B, the heating body 22 has an elongated heat generating substrate 22 that generates heat when energized. A surface protective layer (insulating layer) 22h is provided on the surface of the heat generating substrate 22a (the surface on the pressure roller 24 side (film sliding surface)). The surface protective layer 22h is provided so as to cover a region in contact with the inner peripheral surface (inner surface) of the film 23 on the surface of the heat generating substrate 22a.

  On the back surface (surface opposite to the pressure roller 24 (non-film sliding surface)) of the heat generating substrate 22a, a temperature detecting element (temperature detecting means) 22i such as a thermistor is provided. The temperature measuring element 22i is arranged in a region (a paper passing region (hereinafter referred to as a paper passing portion)) through which the recording material P of the heating body 22 passes. The heating substrate 22 quickly heats up the heat generating substrate 22a by supplying power. The temperature detecting element 22i detects the temperature of the heat generating substrate 22a. The MPU 31 (see FIG. 5A) as a control means takes in the output signal (temperature detection signal) of the temperature measuring element 22i. The MPU 31 controls a predetermined power supply circuit (not shown) based on the output signal to maintain the temperature of the heating element 22 at a predetermined fixing temperature (target temperature).

  The film 23 is a single layer film having a total thickness of 100 μm or less, preferably 60 μm or less and 20 μm or more, or a release layer on the surface of the base film in order to reduce the heat capacity and improve the quick start property of the apparatus. It is a coated composite layer film. The form of the single layer film or the base film is an endless belt shape (cylindrical shape). As a material for the single layer film, PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether), PPS, etc. having heat resistance, releasability, strength, durability and the like are used. As a material for the base film, polyimide, polyamideimide, PEEK (polyetheretherketone), PES (polyethersulfone), or the like is used. As a material for the release layer, PTFE / PFA / FEP (tetrafluoroethylene-perfluoroalkyl vinyl ether) or the like is used.

  The pressure roller 24 is provided with a round shaft-shaped metal core 24a made of a material such as iron or aluminum, an elastic layer 24b provided on the outer periphery of the metal core 24a, and an outer periphery of the elastic layer 24b. It consists of a release layer 24c and the like. For the elastic layer 24b, a general heat-resistant rubber elastic material such as silicone rubber or fluorine rubber can be used. Both materials have sufficient heat resistance and durability when used in the fixing device 6 and have favorable elasticity (softness). Accordingly, silicone rubber or fluororubber is suitable as the main material of the rubber elastic layer 24b. A typical example of the silicone rubber is an addition reaction type dimethyl silicone rubber obtained by crosslinking a dimethylpolysiloxane with an addition reaction between a vinyl group and a silicon-bonded hydrogen group. A typical example of the fluororubber is a binary radical-reactive fluororubber obtained by crosslinking a rubber by a radical reaction with peroxide using a binary copolymer of vinylidene fluoride and hexafluoropropylene as a base polymer. . A typical example is a ternary radical-reactive fluororubber obtained by crosslinking a rubber by radical reaction with peroxide using a terpolymer of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene as a base polymer. it can.

  The release layer 24c may be formed by covering the elastic layer 24b with a PFA tube, or may be formed by coating a fluorine resin such as fluororubber or PTFE, PFA, FEP on the elastic layer. . The thickness of the release layer 24c is not particularly limited as long as it can provide the release roller 24 with sufficient release properties, but is preferably 20 to 100 μm.

  Furthermore, a primer layer or an adhesive layer may be formed between the elastic layer 24b and the release layer 24c for the purpose of adhesion, energization, and the like.

  The film 23 is driven by the rotation of the pressure roller 24 at least when the pressure roller 24 is rotated counterclockwise as indicated by the arrow b at the time of image formation. That is, when the pressure roller 24 rotates, a rotational force acts on the film 23 by the frictional force between the surface of the pressure roller 24 and the surface of the film 23 at the nip portion N. When the film 23 is rotating, the film 23 slides with the inner surface of the film 23 in contact with the surface protective layer 22 h of the heating body 22 at the nip portion N. In this case, in order to reduce the sliding resistance between the inner surface of the film 23 and the surface protective layer 22h of the heating body 22, a lubricant such as heat resistant grease may be interposed therebetween.

  Then, the recording material P carrying the unfixed toner image (image) t is nipped in the state where the film 23 is rotated by the rotation of the pressure roller 24 and the heating body 22 rises to a predetermined fixing temperature and is temperature-controlled. Part N is introduced. The recording material P is nipped and conveyed at the nip portion N by the surface of the film 23 and the surface of the pressure roller 24. During the conveyance process, the heat of the heating body 22 is applied to the toner image t through the film 23 and the nip pressure of the nip portion N is applied. As a result, the toner image t is heated and fixed on the surface of the recording material P. The recording material P exiting the nip portion N is separated from the surface of the film 23 and conveyed, and is discharged from the fixing device 6.

  Further, a flange that only receives the end portion of the film 23 as a film displacement movement restricting means because the tension is not substantially applied to the rotating film 23 other than the nip portion N and the fixing device 6 is simplified. Only members (not shown) are provided.

(3) Heating body 22
Next, the configuration, material, manufacturing method, and the like of the heating body 22 will be described.

  In FIG. 5, (a) is an explanatory diagram of an example of the heating body 22, and is a structural model diagram on the back side of the heating body 22. (B) is a structural model figure of the surface side of the heating body 22 of (a). (C) is sectional drawing of the AA surface of the center of the longitudinal direction of the heating body 22 of (b). (D) is sectional drawing of the BB surface showing the relationship between the electrode part 22d for electric power feeding of the heating body 22 of (b), and the connector 25 for electric power feeding.

  The heating body 22 has an elongated heat generating substrate 22a that generates heat when energized. The heat generating substrate 22a is made of a ceramic resistance heating element having heat resistance and predetermined electrical conductivity. On the back surface (on the heat generating substrate) of the longitudinal end portion of the heat generating substrate 22a, the power supplying electrode portions 22d and 22e for supplying power to the heat generating substrate 22a and the power supplying electrode portions 22d and 22e are electrically connected respectively. Conductive patterns 22f and 22g are provided as conductive portions. 22h is a surface protective layer as an insulating layer. The surface protective layer 22h is provided so as to cover at least a part of the surface of the heat generating substrate 22a, that is, a region in contact with the inner surface of the film 23 on the surface of the heat generating substrate 22a. That is, the surface of the heat generating substrate 22a is at least partially covered with the surface protective layer 22h. The surface protective layer 22h may be provided not only in the region in contact with the inner surface of the film 23 on the surface of the heat generating substrate 22a but also in the entire region of the surface of the heat generating substrate 22a.

  A conductive pattern 22f is electrically connected on the back surface of the heat generating substrate 22a to the power supply electrode portion 22d provided at one end in the longitudinal direction of the heat generating substrate 22a, and the length of the heat generating substrate 22a is extended from the power supplying electrode portion 22d. It extends to the direction center C. In addition, a conductive pattern 22g is electrically connected to the power supply electrode portion 22e provided at the other end in the longitudinal direction of the heat generating substrate 22a on the back surface of the heat generating substrate 22a, and the heat generating substrate is connected to the power supply electrode portion 22e. It extends toward the longitudinal center C of 22a. The conductive patterns 22f and 22g are formed in a shape symmetrical with respect to the longitudinal center C of the heat generating substrate 22a. The conductive patterns 22f and 22g respectively have portions 22f1 and 22e1 extending from the approximate center of the power supply electrode portions 22d and 22e toward the longitudinal center C of the heat generating substrate 22a in the short direction of the heat generating substrate 22a. A portion extending from the portion 22f1, 22e1 to the inside of the short-side end of the heat generating substrate 22a from the portion 22f1, 22e1 in the short direction of the heat generating substrate 22a at the tip of the portion 22f1, 22e1 22f2 and 22e2. These portions 22f1, 22e1, 22f2, and 22e2 are all formed in a linear shape that is narrower than the width of the power feeding electrode portions 22d and 22e.

  Here, the power supply electrode portions 22d and 22e, the conductive patterns 22f and 22g, and the heat generation region of the heat generation substrate 22a that generates heat by energization will be described in more detail.

  FIG. 6A is a structural model diagram showing the back side of a conventional heating body (heating member). (B) is a structural model figure showing the back surface side of the heating body 22 of a present Example. In the conventional heating body, the same code | symbol is attached | subjected to the member and part which are common with the heating body 22 of a present Example.

  In the case of the configuration of only the heat generating substrate 22a that generates heat by energization and the power supply electrode portions 22d and 22e as in the heating element 22 of the conventional example shown in FIG. , 22e. The heating body 22 of this conventional example has the same configuration as the heating body 22 of this embodiment, except that it does not have the conductive patterns 22f and 22g like the heating body 22 of this embodiment.

  On the other hand, in the case of the configuration having the heat generating substrate 22a, the power supply electrode portions 22d and 22e, and the conductive patterns 22f and 22g as in the heating body 22 of this embodiment shown in FIG. 6B, the heat generating substrate 22a is energized. The heat generation region due to is an H2 region between the conductive patterns 22f and 22g. That is, the region H2 on the longitudinal center side of the heat generating substrate 22a from the conductive patterns 22f and 22g becomes the heat generating region. Hereinafter, the heat generation region is referred to as a heat generation portion.

  This is whether the heat generating portion of the heat generating substrate 22a becomes the H2 region or longer depending on the relationship between the volume resistivity (specific resistance) of the conductive patterns 22f and 22g and the volume resistivity (specific resistance) of the heat generating substrate 22a. Will be decided. When the volume resistivity of the conductive patterns 22f and 22g is sufficiently low, the heating portion can be located between the conductive patterns 22f and 22g (H2 region) as shown in FIG. A characteristic point of the heating body 23 of the present embodiment is that the heat generating portion H2 can be formed.

  In the heating element 22 shown in FIG. 6B, power is supplied from the power supply circuit to the energizing electrode portions 22d and 22e through the power supply connector 25, and current flows to the heat generating portion H2 through the conductive patterns 22f and 22g. As a result, the temperature of the heat generating portion H2 rises quickly. The temperature of the heat generating portion H2 is detected by a temperature measuring element 22i (see FIG. 5A) provided at the center in the longitudinal direction of the heat generating portion H2 on the back surface of the heat generating substrate 22a. The MPU 31 (see FIG. 5A) takes in the output signal of the temperature measuring element 22i and controls a predetermined power supply circuit (not shown) based on the output signal, whereby the heating body 22 has a predetermined fixing temperature (target temperature). To maintain.

  The power feeding connector 25 includes a power feeding contact 25a made of metal and a mold portion 25b made of a heat resistant resin such as LCP (liquid crystal polymer) (see FIG. 5D). Since the non-sheet passing portion of the heat generating portion H2 (the region where the recording material P of the heat generating portion H2 does not pass (non-sheet passing region)) is a portion that is not originally required for image fixing, the temperature should be lowered. Further, it is very important to lower the temperature of the mold part 25b from the viewpoint of the reliability of the fixing device 6. This is because when the temperature of the non-sheet passing portion of the heat generating portion H2 is excessively raised (non-sheet passing portion temperature rising), the temperature of the mold portion 25b also rises and exceeds the heat resistance temperature of the mold portion 25b. This is because problems such as melting and destruction occur. In this embodiment, LCP having a heat resistant temperature of 250 ° C. is used as the material of the mold part 25b.

Among the non-metallic heating elements such as silicon carbide (SiC), lanthanum chromite (LaCrO ₃ ), carbon (C), etc., the material constituting the heating substrate 22a has a negative resistance temperature coefficient in the range of room temperature to 300 ° C. Those exhibiting characteristics are preferred. Of these, silicon carbide (SiC) is preferred because it is less affected by oxidation and the like, or industrially available. The heat generating substrate 22a of this embodiment is a silicon carbide heat generating element.

  In general, the resistivity of silicon carbide (SiC) rapidly decreases in the temperature range of 800 ° C. or less as the temperature rises due to current generation (NTC characteristics). This reason is said to be because silicon carbide (SiC) is a semiconductor, so that the number of conduction electrons that can be excited from the impurity level to the conductor increases as the temperature rises.

  Here, in order to explain in detail the effect of the above NTC characteristics on the temperature increase of the non-sheet passing portion, a description will be given using a model diagram.

FIG. 7 is a model diagram for explaining the heat generation amount of the sheet passing portion (the region through which the recording material P passes (paper passing region)) and the non-sheet passing portion in the heating portion H2 of the heating body 22 (FIG. 6B). It is. Here, the heat generating part H2 is considered to be divided into four parts of length a (= 55 mm), and in the heat generating part H2, the resistance at the two central parts in the longitudinal direction is r1, and the resistance at the two longitudinal end parts is r2. (If the temperature at the longitudinal center and the longitudinal end are the same, r1 = r2). 2 (r1 + r2) is the total resistance. Assuming that the current flowing through the heat generating portion H2 is i, the heat generation amount q1 of one block at the central portion in the longitudinal direction is i ² × r1, and the heat generation amount q2 at one end in the longitudinal direction is i ² × r2.

  For the sake of simplicity, considering a case where a small size paper having a longitudinal width 2a (= 110 mm) is passed (introduced) into the nip portion N, the portion having a resistance r1 at the central portion in the longitudinal direction is passed through the paper passing portion. The portion where the end resistance is r2 is a non-sheet passing portion. Since the temperature control of the heating body 22 is performed by the temperature measuring element 22i provided in the paper passing portion, the non-paper passing which does not take heat away from the small size paper compared to the paper passing portion where heat is taken away from the small size paper. The temperature of the part rises. Since the heat generating substrate 22a of the present embodiment has NTC characteristics in the actual use temperature range (250 ° C. or lower), r1> r2 when small-size paper is passed. Since the current i is the same in the sheet passing portion and the non-sheet passing portion, q1> q2, and the heat generation amount in the non-sheet passing portion is smaller than the heat generation amount in the sheet passing portion in the central portion in the longitudinal direction. Can be suppressed.

  Next, the manufacturing method of the heating body 22 will be described.

  The following methods are well known as sintering methods for a silicon carbide (SiC) heating element (hereinafter referred to as a silicon carbide (SiC) heating element) which is a material of the heating substrate 22a. For example, a normal pressure sintering method is known in which a sintering aid is added to fine powdered silicon carbide (SiC) and heated and sintered under normal pressure. Also, a reaction firing obtained by forming a mixture of silicon carbide (SiC), carbon (C), and an organic binder, bringing the mixture into contact with molten silicon (Si) at a high temperature, and then adding it to silicon carbide (SiC) secondarily. The law is known. Also known is a recrystallization method in which fine powder silicon carbide (SiC) is molded and sintered at a temperature of 2000 ° C. or higher. In addition, there are known a hot press method in which silicon carbide (SiC) powder in a mold is heated with a heater and simultaneously pressed from above and below, and an HIP method in which sintering is performed under isotropic pressure using a gas pressure.

  As the silicon carbide (SiC) raw material, it is preferable to use silicon carbide (SiC) powder having an average particle size of 5 μm or less. When the average particle diameter exceeds 5 μm, a sufficient driving force for sintering cannot be obtained, and it becomes difficult to obtain a sintered body having a low porosity. Preferably, silicon carbide (SiC) powder having an average particle size of 2 μm or less is used as a raw material.

This silicon carbide (SiC) powder is mixed with a sintering aid, and the resulting mixed powder is molded into a molded body. As the sintering aid, for example, B compounds such as B, B ₄ C, and BN and carbon sources such as carbon black can be used. In order to improve the sinterability, a small amount of Al compound such as Al, Al ₄ C ₃ , Al ₂ O ₃ may be added. Next, if it demonstrates with a normal pressure sintering method, a molded object will be heat-fired to the temperature of 2100-2300 degreeC by nitrogen gas atmosphere. By heating, densification and solid solution of nitrogen proceed simultaneously, and a silicon carbide (SiC) sintered body having a small porosity and good conductivity can be obtained.

  In the atmospheric pressure sintering method in which boron (B) and carbon (C) are added as sintering aids, there is generally a peak of sintering shrinkage around 1950 ° C. However, if nitrogen gas is present in the heating atmosphere during firing, the sinterability of silicon carbide (SiC) decreases and the peak of sintering shrinkage shifts to the high temperature side, so a dense silicon carbide sintered body is obtained. Must be fired at a temperature of 2100 ° C. or higher. When the heating temperature exceeds 2300 ° C., sublimation of silicon carbide (SiC) starts and an extreme increase in resistance tends to occur.

  A silicon carbide (SiC) heating element is molded to form the heating substrate 22a. The power supply electrode portions 22d and 22e and the conductive patterns 22f and 22g are formed at both longitudinal ends of the heat generating substrate 22a using a conductive paste mainly composed of silver (Ag), platinum (Pt), gold (Au), and the like. It is formed. That is, the good conductive film of the conductive paste is formed on the heat generating substrate 22a with a thickness of about 5 μm to 100 μm by screen printing. The power supply electrode portions 22d and 22e and the conductive patterns 22f and 22g are not limited to the conductive paste, but may be a conductive paste mainly composed of silver / platinum (Ag / Pt) alloy, silver / palladium (Ag / Pd) alloy, or the like. Good. Thereafter, the coating film is dried and baked in a baking furnace at a baking peak temperature of about 850 ° C. for about 10 minutes (baking furnace elapsed time is about 40 minutes). Since the power supply electrode portions 22d and 22e and the conductive patterns 22f and 22g are provided for supplying power to the heat generating portion H2 of the heat generating substrate 22a, the resistance is sufficiently lower than that of the heat generating substrate 22a. The power supply electrode portions 22d and 22e and the conductive patterns 22f and 22g may be formed on either the front surface side or the back surface side of the heat generating substrate 22a, and may be appropriately selected as necessary. Moreover, there is no problem in overcoating to obtain a desired thickness.

  The surface protective layer 22h is an overcoat layer of the heat generating substrate 22a, and its main purpose is to ensure electrical insulation with the heat generating substrate 22a and slidability of the film 23. Whether or not the overcoat layer 22h is provided in the heating body 22 according to the configuration of the fixing device 6 may be appropriately selected. Moreover, what is necessary is just to select suitably the structure which covers all the heat generating boards 22a with the overcoat layer 22h, and the structure which only covers one surface (surface or both surfaces) of the heat generating board 22a as needed.

The overcoat layer 22h continuously forms a coating film on the predetermined surface portion of the heat generating substrate 22a without any gap. As the glass paste, for example, silicon oxide silicon oxide as a main component _{(SiO 2) (SiO 2)} - zinc oxide (ZnO) - aluminum oxide _(Al 2 _{O 3)} based glass powder, ethylcellulose (organic binder And kneading with an organic solvent. And after drying this coating film, it is fired in a firing furnace at a firing peak temperature of about 850 ° C. for about 10 minutes (baking furnace elapsed time is about 40 minutes), and a glassy overcoat having a thickness of 15 μm to 100 μm. Layer 22h is obtained. There is no problem in applying the overcoat layer 22h as appropriate in accordance with the thickness required for the overcoat layer 22h.

  The constituent material and manufacturing method of the heat generating substrate 22a are not limited to those described above. For example, as a silicon carbide (SiC) heating element, a molded product obtained by processing a material having a trade name shown in the following a), b), c) into a necessary shape may be obtained.

A): Made by Bridgestone Corporation, trade name: Pure Beta-R
Volume resistivity: About 1 × 10 ^-1 Ω · cm (25 ° C environment) by four-probe method
Resistance temperature coefficient: about −3000 ppm / ° C. in the range of room temperature (25 ° C.) to 225 ° C.
B): manufactured by Bridgestone Corporation, product name: Pure Beta-R modified product, volume resistivity: about 1 × 10 ⁻² Ω · cm (25 ° C. environment) by the four-probe method
Resistance temperature coefficient: about −3000 ppm / ° C. in the range of room temperature (25 ° C.) to 225 ° C.
That is, the resistance temperature coefficient of Pure Beta-R, which is a constituent material of the heat generating material portion, is negative in the range from about room temperature (25 ° C.) to 200 ° C. Here, the temperature coefficient of resistance in the present embodiment will be described. For the resistance temperature coefficient, the resistance value R1 in the 25 ° C. environment and the resistance value R2 in the furnace 225 ° C. environment are measured for the resistance value between the long side ends of the conductive substrate portion 22a, and the resistance change rate per unit temperature change Is a value calculated by the following equation.

(R2-R1) / R1 / (225 ° C.-25 ° C.) × 10 ⁶ [ppm / ° C.]
C): Tokai Koetsu Kogyo Co., Ltd., trade name: Elema Volume resistivity: about 1 × 10 ⁻¹ Ω · cm
Resistance temperature coefficient: about −1500 ppm / ° C. in the range of room temperature (25 ° C.) to 225 ° C.
Here, the volume resistivity of the silicon carbide (SiC) -based heating element that can be used as the heating element 22 used in the fixing device (fixing device) is preferably suppressed to 3 × 10 ⁻¹ Ω · cm or less. If the volume resistivity is higher than that, it is necessary to make the length of the heat generating substrate 22a short in the short direction or to increase the thickness of the heat generating substrate 22a. Alternatively, if the dimensions of the heat generating substrate 22a are made standard, there arises a problem that the heat generating substrate 22a does not generate heat.

On the other hand, as the lower limit side of the volume resistivity, it should be noted that although the volume resistivity is too low, the volume resistivity is too low to generate heat. The above-mentioned volume resistivity of 1 × 10 ⁻² Ω · cm of the Bridgestone pure beta-R improved product has been confirmed to generate heat at the substrate size described later, and there is no problem.

In the volume resistivity range, the volume resistivity of the conductive patterns 22f and 22g is preferably 1 × 10 ⁻⁴ Ω · cm or less, so that the heat generation region of the heat generating substrate 22a is located between the conductive patterns 22f and 22g (heat generating portion H2 ). More preferably, the volume resistivity of the conductive patterns 22f and 22g is 1 × 10 ⁻⁵ Ω · cm or less.

(4) Evaluation Next, the shape and characteristics of the heating body 22 of the first embodiment will be described in more detail.

  The effects of the heating element 22 of this example were confirmed using the heating elements configured as in Example 1, Example 2 and Comparative Example below. In the heating body shown in Example 1, Example 2, and the comparative example, the same code | symbol is attached | subjected to the member and part which are common in the heating body 22 of a present Example.

Example 1
FIG. 8 is an explanatory diagram of the heating body 22 according to the first embodiment. 8A is a diagram showing the configuration of the heat generating substrate 22a and the power supply electrode portions 22d and 22e and the conductive patterns 22f and 22g provided on the back surface of the heat generating substrate 22a, and FIG. 8B is an overcoat provided on the surface of the heat generating substrate 22a. It is a figure showing the layer 22h.

  In the heating body 22 shown in Example 1, as the heating substrate 22a, the above-described Pure Beta-R improved product manufactured by Bridgestone Co., Ltd. and formed into a width of 5 mm, a length of 270 mm, and a thickness of 0.5 mm was used.

  On the back surface (non-film sliding surface) of the heat generating substrate 22a, the power supply electrode portions 22d and 22e and the conductive patterns 22f and 22g were formed with a thickness of 10 μm using silver (Ag). At this time, the length of the heat generating portion H2 formed between the conductive patterns 22f and 22g was 220 mm. An overcoat layer 22h was formed to a thickness of 50 μm on the surface (film sliding surface) of the heat generating substrate 22a. In addition, also in the heating body of Example 2 and the heating body of the comparative example which will be described below, the thickness of the energizing electrode portion, the conductive pattern, and the overcoat layer is the same as that of the heating body of this embodiment.

Example 2
FIG. 9 is an explanatory diagram of the heating body 22 according to the second embodiment. 9A is a diagram showing the configuration of the heat generating substrate 22a and the power supply electrode portions 22d and 22e and the conductive patterns 22j and 22k provided on the back surface of the heat generating substrate 22a, and FIG. 9B is an overcoat provided on the surface of the heat generating substrate 22a. It is a figure showing the layer 22h.

  The heating body 22 shown in the second embodiment has the same configuration as the heating body 22 of the first embodiment except that the shapes of the conductive patterns 22j and 22k are changed. The conductive pattern 22j has a portion 22j1 extending from the approximate center of the power supply electrode portion 22d toward the longitudinal center of the heat generating substrate 22a. A portion 22j2 having an α1 portion and an α2 portion wider than the portion 22j1 is formed at the tip of the portion 22j1. The conductive pattern 22k has a portion 22k1 extending from the approximate center of the power supply electrode portion 22e toward the longitudinal center of the heat generating substrate 22a. And the part 22k2 which has (beta) 1 part and (beta) 2 part wider than this part 22k1 in the front-end | tip of the part 22k1 is formed. The length of the heat generating part H2 formed between the conductive patterns 22j and 22k is 220 mm. Here, a current flows from the α1 portion of the conductive pattern 22j to β1 of the conductive pattern 22k, and a current flows from the α2 portion of the conductive pattern 22j to β2 of the conductive pattern 22k. In this case, the amount of heat generated at the end of the heat generating substrate (the end of the substrate in the short direction) is high in the short direction of the heat generating substrate 22a. In general, the heat generating substrate end is subject to temperature sag due to a heat dissipation phenomenon, but the structure of the heating body 22 of the second embodiment has a small temperature gradient in the short direction of the heat generating substrate 22a, and in the short direction of the heat generating substrate 22a. There is an advantage that there is little thermal stress.

Comparative Example FIG. 10 is an explanatory diagram of a heating body 22 according to a comparative example. FIG. 10A is a diagram showing the configuration of the heat generating substrate 22a and the feeding electrode portions 22d and 22e provided on the back surface of the heat generating substrate 22a, and FIG. 10B is a diagram showing the overcoat layer 22h provided on the surface of the heat generating substrate 22a. is there.

  The heating body 22 shown in the comparative example has the same configuration as the heating body 22 of Example 1 except that there is no conductive pattern. The length of the heat generating portion H2 formed between the power feeding electrode portions 22d and 22e is 248 mm.

About each heating body 22 of Example 1, Example 2, and a comparative example, connector part temperature (power supply connector mold part temperature) was compared. The fixing device on which each heating body 22 is mounted has the same configuration. An image forming apparatus (printer) on which the fixing device is mounted has the same configuration. In the image forming apparatus, the contact point of the power supply connector 25 when 200 sheets of A4 size recording material (basis weight 128 g / mm ² ) are continuously fed from the state in which the fixing device is sufficiently adapted to room temperature (25 ° C.). The temperature of the power supply connector mold part 25b in contact with the part 25a was measured. The input voltage was 120V and the fixing temperature was 200 ° C. The results are shown in Table 1.

  FIG. 11 is an explanatory diagram of the heat generating portion H2 of the heating body 22 and the non-sheet passing portion of the A4 size recording material in the first embodiment. FIG. 12 is an explanatory diagram of the heat generating portion H2 of the heating body 22 and the non-sheet passing portion of the A4 size recording material in the second embodiment. FIG. 13 is an explanatory diagram of the heat generating portion H2 of the heating body 22 of the comparative example and the non-sheet passing portion of the A4 size recording material.

  As shown in Table 1, the heating body 22 of Example 1 was able to suppress the temperature of the power supply connector mold portion 25b to a temperature of 175 ° C., which is no problem in actual use. This is thought to be due to the following reasons. The protrusion amount (non-sheet passing portion) L1 of the heat generating portion H2 of the silicon carbide (SiC) heating element 22a is 5 mm on one side with respect to the longitudinal width 210 mm of the A4 size recording material in the longitudinal direction of the heat generating substrate 22a. (See FIG. 11).

  The heating body 22 of the second embodiment is the same as the heating body 22 of the first embodiment in that the amount of protrusion of the heating portion H2 of the silicon carbide heating element 22a is 5 mm on one side (see FIG. 12).

  In the heating body 22 of the second embodiment, the heat generation area in the short direction of the heat generation substrate 22a is provided between the power supply electrode portions 22d and 22e and the conductive patterns 22j and 22k connected to the power supply electrode portions 22d and 22e. However, it is less than the heating body 22 of the first embodiment. For this reason, in the heating body 22 of Example 2, it is considered that the temperature of the power supply connector mold portion 25b is lower than that of the heating body 22 of Example 1.

  As shown in FIG. 13, in the heating body 22 of the comparative example, the protruding amount L2 of the heat generating portion H2 of the heat generating substrate 22a is 19 mm on one side. In other words, by forming the feeding electrode portions 22d and 22e with a length of 5 mm and a width of 5 mm at a position 1 mm inside from the edge of the longitudinal end portion of the heat generating substrate 22a, the amount of protrusion of the heat generating portion H2 (non-sheet passing portion) L2 is 19 mm on one side. Therefore, the length of the heat generating portion H2 formed between the power feeding electrode portions 22d and 22e is 248 mm.

  Further, the connector portion 25 and the heat generating portion H2 of the heat generating substrate 22a are in contact with each other.

  The temperature of the power supply connector mold portion 25b is 262 ° C. for two reasons: the protrusion amount L2 of the heat generating portion H2 is 19 mm on one side, and the connector portion 25 and the heat generating portion H2 of the heat generating substrate 22a are in contact with each other. The temperature was very high. Since the mold part 25b of the connector part 25 exceeded the heat resistance temperature (250 ° C.), some deformation was observed.

  As described above, in the heating body 22 of this embodiment, the heat generating portion H2 is formed by providing the power supply electrode portions 22d and 22e and the conductive patterns 22f and 22g on the elongated heat generating substrate 22a exhibiting the NTC characteristics. Accordingly, it is possible to suppress an excessive temperature rise (non-sheet passing portion temperature rise) in a region where the recording material of the heat generating portion H2 does not pass by taking advantage of the NTC characteristics. Further, since the power supply electrode portions 22d and 22e and the conductive patterns 22f and 22g are provided on the heat generating substrate 22a, the power supply electrode portions 22d and 22e can be separated from the heat generating portion H2, and the power supply electrode of the heat generating substrate 22a can be separated. The temperature rise around the portions 22d and 22e can be suppressed.

[Other]
1) The fixing device of the embodiment is not limited to the printer that transports the recording material on the basis of the central transport, and may be mounted on a printer that transports the recording material on the basis of the one-side transport. Here, the one-side conveyance reference refers to a conveyance form in which the recording material P is conveyed with reference to one end surface in the width direction of the recording material P.

  2) The image heating apparatus of the present invention is not limited to the heat-fixing apparatus of the embodiment, and is widely used such as an image heating apparatus that heats a recording material carrying an image to improve the surface properties such as gloss, and an image heating apparatus that is supposed to be worn. It can be used as a means / device for heat-treating a recording material carrying an image.

Schematic model diagram of an example of an image forming apparatus Cross-sectional configuration model diagram of an example of a fixing device Vertical cross-section configuration model diagram of fixing device View of fixing device from recording material introduction side Illustration of an example of a heating element Explanatory drawing of the heat_generation | fever area | region (heat-generation part) of the conventional heating body and the heat_generation | fever area | region (heat-generation part) of the heating body of a present Example Model diagram for explaining the heat generation amount of the paper passing part and the non-paper passing part in the heating part of the heating element Explanatory drawing of the heating body which concerns on Example 1. Explanatory drawing of the heating body which concerns on Example 2. Explanatory drawing of the heating body which concerns on a comparative example Explanatory drawing of the heat_generation | fever part of a heating body which concerns on Example 1, and a non-sheet passing part Explanatory drawing of the heat_generation | fever part of a heating body which concerns on Example 2, and a non-sheet passing part Explanatory drawing of the heat_generation | fever part and non-sheet passing part of the heating body which concerns on a comparative example

Explanation of symbols

22: Heating element, 22a: Heat generating substrate, 22d, 22e: Feeding electrode, 22f, 22g: Conductive pattern, 23: Heat resistant film, H2: Heat generating area, P: Recording material, N: Nip, t: Unfixed Toner image

Claims (6)

A heating member used in an image heating apparatus that heats an image carried on a recording material, the elongated heating substrate generating heat when energized, and the heat generation provided on the heating substrate at a longitudinal end of the heating substrate In a heating member having an electrode part for supplying power to the substrate,
A conductive portion electrically connected to the electrode portion and extending from the electrode portion toward the longitudinal center of the heat generating substrate is provided on the heat generating substrate, and is located closer to the longitudinal center side of the heat generating substrate than the conductive portion. A heating member having a heat generating region in the region.   The heating member according to claim 1, wherein the heating substrate is a ceramic resistance heating element.   The heating member according to claim 1, wherein the temperature coefficient of resistance of the heat generating substrate is negative in a range of room temperature to 200 ° C.   The heating member according to claim 1, wherein the heating substrate is a silicon carbide heating element.   The heating member according to claim 1, wherein at least a part of the heat generating substrate is covered with an insulating layer. A heating member having an elongated heating substrate that generates heat when energized, an electrode portion provided on the heating substrate at a longitudinal end portion of the heating substrate for supplying power to the heating substrate, and moves while being in contact with the heating member An image heating apparatus that heats an image carried on a recording material via the flexible member by heat generation of the heat generating substrate,
The heating member has a conductive portion on the heat generating substrate that is electrically connected to the electrode portion and extends from the electrode portion toward the longitudinal center of the heat generating substrate. An image heating apparatus having a heat generation area in a central area in the longitudinal direction.