JP6739957B2 - Heater and fixing device - Google Patents

Description

The present invention relates to a heater used for heating an image on a recording material, and a fixing device including the heater. The heater and fixing device of the present invention can be used in an image forming apparatus such as a copying machine, a printer, a fax machine, and a multi-function machine having a plurality of these functions.

2. Description of the Related Art Conventionally, a method of fixing a toner image on a recording material by applying heat and pressure with a fixing device after forming a toner image on the recording material is generally used in image forming apparatuses. On the other hand, in response to recent demands for energy saving and quick start, a fixing device of a system in which a heater is brought into contact with the inner surface of a thin belt to heat the belt has been proposed (Patent Document 1).

Further, Patent Document 1 discloses a configuration in which a region in which a heater generates heat (heat generation width) is changed according to a width size of a recording material to be heated. FIG. 11 is a circuit diagram of the heater 1006 in the fixing device described in Japanese Unexamined Patent Application Publication No. 2004-242242.

In this heater 1006, electrodes 1027 (1027a to 1027f) are arranged side by side in the longitudinal direction of the substrate 1021, and the resistance heating layers 1025 (1025a to 1025e) are energized by each electrode to heat the resistance heating layers 1025. Further, each electrode of the heater 1006 is connected to the wiring layer 1029 (1029a, 1029b) formed on the substrate. Specifically, the wiring layer 1029b connected to the electrodes 1027b and 1027d extends to one end in the longitudinal direction of the substrate. The wiring layer 1029a connected to the electrodes 1027c and 1027e extends to the other end in the longitudinal direction of the substrate.

Further, the electrode 1027a and the wiring layer 1029b can be connected to the wiring member at one end in the longitudinal direction of the substrate, and the electrode 1027f and the wiring layer 1029a can be connected to the wiring member at the other end in the longitudinal direction of the substrate. Has become. An insulating layer for protecting each wiring is not provided at both ends in the longitudinal direction of the substrate, and the wiring layers 1029a and 1029b and the electrodes 1027a and 1027f are exposed. Therefore, the resistance heating layer 1025 is connected to the power supply circuit by the wiring member contacting the exposed portions of the wiring layers 1029a and 1029b and the electrodes 1027a and 1027f.

The power supply circuit includes an AC power supply and a switch 1033 (1033a, 1033b, 1033c, 1033d), and the connection pattern of each wiring can be changed by turning the switch 1033 on and off. That is, the wiring layers 1029a and 1029b are connected to either the power supply terminal 1031a side or the power supply terminal 1031b side according to the connection pattern in the power supply circuit, and the resistance heating layer 1025 of the resistance heating layer 1025 is connected according to the width size of the recording material to be heated. The heat generation area (heat generation width) is changed.

For example, as shown in FIG. 11A, in the case of a connection pattern in which the switches 1033a and 1033b are on and the switches 1033c and 1033d are off, all the resistance heating layers 1025a to 1025e generate heat. In the case of the connection pattern in which the switches 1033a and 1033b are off and the switches 1033c and 1033d are on as in (b), the resistance heating layers 1025b, 1025c, and 1025d generate heat.

JP, 2012-37613, A

By the way, in Patent Document 1, it is not described where in the heater longitudinal direction the thermistor, which is a temperature sensor (temperature detecting means) for detecting the heater temperature, is arranged, but the thermistor is provided in the longitudinal direction of the heater. is there. However, in a heater whose longitudinal heat distribution can be changed independently, if the number of thermistors arranged in the heater is one, the temperature of each heating element cannot be detected. Therefore, when the temperature of the heater rises abnormally, the life of the belt portion corresponding to the abnormal temperature rise may be shortened.

An object of the present invention is to prevent an abnormal temperature rise in a heater that can change the area where the resistance heating element generates heat according to the width size of the recording material to be heated. Another object of the present invention is to provide a fixing device capable of preventing an abnormal temperature rise of the heater.

Typical configuration of the heating data in accordance with the present invention for achieving the above Symbol purpose of, a heater used in the fixing apparatus for heating an image on a recording material, an elongated substrate, along the length of the substrate A resistance heating element which is extended to generate heat by energization, a plurality of electrodes provided on the substrate, a plurality of conductor paths extending from each of the plurality of electrodes, and a plurality of conductor paths. A plurality of branch paths branching from each of the resistance heating elements at intervals along the longitudinal direction, the resistance heating elements being electrically connected to the resistance heating elements across the resistance heating elements. the along a longitudinal comprises a branch passage which is divided into a plurality of small sections heating portion, a small section fever that written in a region width corresponding to the width size in accordance with the width size of the recording material conveyed In a heater in which a voltage is selectively applied to the plurality of electrodes so that the portion heats up, the length of the resistance heating element is within the region of the small section heating unit corresponding to the end of the region width. An end temperature sensor that is provided outside the region width in the direction and detects the temperature of a small section heat generating portion corresponding to the end of the region width, and an end of the region width in the longitudinal direction of the resistance heating element. An outside temperature sensor for detecting the temperature of the small section heat generating portion adjacent to the end of the area width and outside the small section heat generating portion corresponding to The outside temperature sensor detects the temperature of the inner end portion in the longitudinal direction of the resistance heating element in the area of the small-section heat generating portion adjacent to the small-section heat generating portion corresponding to the end portion of the area width. And

According to the present invention, it is possible to prevent the abnormal temperature rise in the heater, which can change the area where the resistance heating element generates heat according to the width size of the recording material to be heated. Further, it is possible to provide a fixing device capable of preventing the abnormal temperature rise of the heater.

Schematic diagram of the heater of Example 1 Explanatory drawing of the basic configuration of the heater (No. 1) Explanatory drawing of the basic configuration of the heater (Part 2) Schematic diagram illustrating the heating method of the heater and the switching method of the heating width 1 is a schematic configuration diagram of an image forming apparatus (printer) in Embodiment 1. (A) is a schematic cross-sectional view of a main part of the fixing device in Embodiment 1, and (b) is a schematic diagram of the layer structure of the fixing belt. A schematic vertical sectional front view of the fixing device with an intermediate part omitted Schematic diagram of the configuration of the heater of Example 2 Diagram for explaining failure examples Diagram for explaining the temperature detected by the end thermistor and the outer end thermistor Conventional heater circuit diagram

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

<<Example 1>>
[Image forming device]
FIG. 5 is a schematic sectional view of the printer 1 in this embodiment. The printer 1 is a tandem-intermediate transfer type full-color printer, and is an image of each color toner of yellow (Y), magenta (M), cyan (C), and black (Bk) (hereinafter, toner image). 4) forming four image forming units UY, UM, UC, and UBk.

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

Toner images of respective colors are superposed in a predetermined manner on the intermediate transfer belt 8 rotating from the drum 2 of each image forming section and are primarily transferred. As a result, a four-color superimposed toner image is formed on the belt 8. On the other hand, one recording material (sheet, paper) P is fed from the cassette 9 or 10 or the manual feed tray 11, passes through the transport path 12, and presses the belt 8 and the secondary transfer roller 13 at a predetermined control timing. Is introduced into the secondary transfer nip portion. As a result, the four-color superimposed toner images on the belt 8 are secondarily transferred onto the recording material P all together. The recording material P is introduced into the fixing device 40 and undergoes a toner image fixing process.

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

In the case of the double-sided image forming mode, the recording material P exiting the fixing device 40 is once guided to the side of the conveying path 15 by the control of the flapper 14 and then is switchback conveyed to be introduced to the side of the double-sided conveying path 19. Then, in the state of being turned upside down, the toner image is formed again on the other surface by passing through the conveying path 12 and being introduced into the secondary transfer nip portion. After that, as in the case of single-sided image formation, the sheet is introduced into the fixing device 40 and discharged to the discharge tray 16 or 18 as a double-sided image formed product.

In the printer 1 according to the present embodiment, the recording material P of various sizes including small and large widths is conveyed based on a so-called center reference of the recording material width center. Hereinafter, the recording material having the maximum width size usable in the apparatus will be referred to as a large-sized recording material, and the recording material having a width smaller than that will be referred to as a small-sized recording material. The image forming apparatus of this embodiment can produce 30 sheets of A4 horizontal size recording material per minute.

[Fixing device]
Next, the fixing device 40 in this embodiment will be described. 6A is a schematic cross-sectional view of a main part of the fixing device 40, and FIG. 6B is a schematic diagram of the layer structure of the fixing belt. FIG. 7 is a schematic vertical sectional front view of the main part of the fixing device 40 with the middle part omitted. The front surface of the fixing device 40 is the surface viewed from the recording material introduction side.

The fixing device 40 is a belt heating type image heating device, and is roughly classified into a belt unit 60 for heating an image on the recording material P and an elastic pressure roller 70 as a facing member (nip forming member , pressure member ). , And a device housing 41 that accommodates them.

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

The belt unit 60 is a unit for heating and pressing the image on the recording material P, is provided so as to be substantially parallel to the pressure roller 70, and has a heater 600, a heater holder 601, a support stay 602, and a belt 603.

The heater 600 presses the belt 603 toward the pressure roller 70 so that the nip portion N has a desired width in the recording material conveyance direction a. Further, the heater 600 includes a substrate 610 and a resistance heating element 620 (resistance heating layer: hereinafter referred to as a heating element) that generates heat on the substrate 610 when energized, and is fixed to a recess 601 a on the lower surface of the heater holder 601. In this embodiment, the heating element 620 is provided on the back side of the substrate 610 (the side that does not contact the belt 603). However, the invention is not limited to this, and may be provided on the front surface side (the side in contact with the belt 603).

A polyimide layer (not shown) having a thickness of about 10 μm is provided as a sliding layer on the surface side of the substrate 610 that is in contact with the belt 603, and by reducing the sliding resistance between the belt 603 and the heater 600. The wear of the inner surface of the belt 603 can be suppressed. Further, a lubricant such as grease may be applied to the inner surface of the belt 603 to reduce the rubbing resistance.

The belt 603 is a cylindrical belt (endless belt) for heating and pressing the toner image T on the recording material P at the nip portion N. In this embodiment, as shown in the schematic layer structure of FIG. 6B, a base material 603a provided with an elastic layer 603b and a release layer 603c is used. Specifically, as the base material 603a, a cylindrical member made of a nickel alloy having an outer diameter of 30 mm, a length (width) of 340 mm, and a thickness of 30 μm is used. Furthermore, a silicone rubber layer having a thickness of 400 μm is formed as an elastic layer 603b on the base material 603a, and a fluororesin tube having a thickness of about 20 μm is coated as a release layer 603c on the elastic layer 603b.

The heater holder 601 (hereinafter referred to as the holder 601) is a member that holds the heater 600 while pressing it toward the belt 603. Further, the holder 601 has a substantially semi-circular cross-sectional shape and has a function of restricting the rotation trajectory of the belt 603. A highly heat-resistant resin or the like is used for the holder 601, and Zenite 7755 (trade name) manufactured by DuPont is used in this embodiment.

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

As shown in FIG. 7, the support stay 602 is supported by the flanges 411a and 411b at both ends in the longitudinal direction. The flanges 411a and 411b are collectively referred to as a flange 411. The flange 411 regulates the movement of the belt 603 in the longitudinal direction and the shape in the circumferential direction. A heat-resistant resin or the like is used for the flange 411, and PPS (polyphenylene sulfide) is used in this embodiment. A pressure spring 415(a,b) is provided between the flange 411 and the pressure arm 414(a,b) in a contracted state.

With the above configuration, the elastic force of the pressure spring 415 is transmitted to the heater 600 via the flange 411, the support stay 602, and the holder 601. Then, the belt 603 is pressed against the pressure roller 70 with a predetermined pressing force, and a nip portion N having a predetermined width is formed in the recording material conveyance direction a. In the present embodiment, the pressing force is about 156.8 N on each of the one end side and the other end side, and the total pressing force is about 313.6 N (32 kgf).

Further, the connector 700 (a, b) is a power feeding member electrically connected to the heater 600 for applying a voltage to the heater 600, and is detachably attached to both ends of the heater 600 in the longitudinal direction.

The pressure roller 70 is a driving rotator that cooperates with the belt 603 to form a nip portion N for heating the toner image T on the recording material (on the sheet) and rotationally drive the belt 603. The pressure roller 70 has a multi-layer structure in which an elastic layer 72 is provided on a metal cored bar 71, and a release layer 73 is further provided on the elastic layer 72. As the core metal 71, stainless steel, SUM (sulfur and sulfur composite free-cutting steel material), or aluminum can be used. As the elastic layer 72, silicone rubber, sponge rubber layer, or elastic foam rubber can be used. As the release layer 73, a fluororesin material can be used.

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

As shown in FIG. 7, both ends of the core metal 71 of the pressure roller 70 have bearings 42 (a, b) between one end side and the other end side plate 41 (a, b) of the apparatus casing 41, respectively. It is rotatably held through. A gear G is provided at one end of the cored bar 71 to transmit the driving force of a motor (driving source) M controlled by the control circuit (control section) 100 to the cored bar 71.

The pressure roller 70 driven by the motor M rotates in the direction of arrow R70 in FIG. 6, and the driving force is transmitted to the belt 603 at the nip portion N to rotate the belt 603 in the direction of arrow R603. In this embodiment, the control circuit 100 controls the motor M so that the surface speed of the pressure roller 70 is 200 mm/sec.

As described above, the pressure roller 70 is rotationally driven by the driving of the motor M, and the belt 603 is driven to rotate accordingly. Then, as will be described later, energization control to the heater 600 is performed so that the resistance heating element region generates heat in accordance with the width size of the recording material P to be heated, and the heating region of the heater 600 is raised to a predetermined temperature. Temperature controlled.

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

[heater]
Next, the configuration of the heater 600 will be described in detail. First, the heating method and the heating width switching method of the heater will be described with reference to the schematic diagram of FIG. As shown in (a), the branch paths 715a, 715b, and 715c are connected to the first conductor path 710. On the other hand, branch paths 725d, 725e, 725f are connected to the second conductor path 720. The branch paths 715a, 715b, 715c connected to the first conductor path 710 and the branch paths 725d, 725e, 725f connected to the second conductor path 720 are alternately arranged in the longitudinal direction, and a heating element is provided between the branch paths. 620 is provided to be electrically connected.

When the voltage V is applied between the first conductor path 710 and the second conductor path 720, a potential difference is generated between the adjacent branch paths, and the heating element 620 generates heat (lights) due to the generation of the current indicated by the arrow in the figure. To do. Further, as shown in (b), when a switch SW is provided between the branch paths 725e and 725f and the switch SW is turned off, the branch paths 715b and 715c have the same potential, so that the heating element between the branch paths 715b and 715c is generated. 620 does not generate heat.

That is, by cutting the electrical connection of a part of the conductor path, only a part of the heating element can generate heat. When a plurality of heat generating elements arranged in the longitudinal direction are energized to generate heat, it is preferable that the branch paths are arranged so that the current directions of the adjacent heat generating elements are staggered.

As another arrangement of the heating element and the second branch path, there is a configuration in which branch paths having different polarities are connected to both ends of the heating element so that the directions of currents are the same in the longitudinal direction. However, since two branch paths are required between the adjacent heating elements, a short circuit may occur between the branch paths. In addition, since the width of the branch passage between the heating elements is widened, the non-heat generating portion becomes large, and temperature unevenness occurs in the heater and the belt in the longitudinal direction. Therefore, it is desirable to arrange the heating element and the branch path so as to also serve as the branch path between the adjacent heating elements.

Next, the basic configuration of the heater 600 of this embodiment will be described in detail with reference to the schematic diagram of FIG. The heater 600 includes an elongated substrate 610, a resistance heating element 620 that extends along the length of the substrate and generates heat when energized, a common electrode 641, and a length from the common electrode 641 to the heating element 620. A common conductor path 640 extending. In addition, a plurality of common branch paths branching from the common conductor path 640 at intervals along the longitudinal direction, the common branch paths crossing the heating element 620 and electrically connected to the heating element 620. It has a path 642 (a to j).

Further, the plurality of individual electrodes 651, 661, 671 and the opposite conductor paths 650, 660(a, b), 670(a, b) extending from the plurality of individual electrodes along the length of the heating element 620, respectively. ) Has. Further, it has a plurality of opposed branch paths 652(a-c), 662(a-d), 672(a, b) branched from each of those opposed conductor paths. These opposing branch paths are alternately arranged with the common branch paths 642 (a to j), cross the heating element 620, and are electrically connected to the heating element 620, and together with the common branch paths 642 (a to j). The heating element 620 is divided into a plurality of small section heating elements (small section heating portions) 620 (a to r) along the length.

In the heater 600 of this embodiment, the common electrode 641 is arranged on one end side of the substrate 610 in the longitudinal direction. A plurality of individual electrodes, in the present embodiment, three individual electrodes 651, 661 and 671 are arranged in parallel on the other end side of the substrate 610 in the longitudinal direction.

Then, excluding the portions of the common electrode 641 and the plurality of individual electrodes 651, 661, 671, the heating element 620 (a to r) and the above-mentioned common conductor path, which is a conductor pattern, common branch path, counter conductor path, counter branch. The part of the road is covered with an insulating coat layer (not shown) as a protective layer. That is, the electrodes 641, 651, 661, and 671 are not provided with an insulating coat layer in order to ensure electrical connection with the connector 700 (a, b), and are outside the heater region that contacts the belt 603 in an exposed state. It is provided in.

The substrate 610 is a member that determines the size and shape of the heater 600, and as the material thereof, a ceramic material such as alumina or aluminum nitride having excellent heat resistance, thermal conductivity, and electrical insulation is used. In this embodiment, alumina having a length in the longitudinal direction of 400 mm, a length in the lateral direction of 8.0 mm, and a thickness of about 1 mm is used.

The heating element 620 and the conductor pattern are formed on the substrate 610 by a screen printing method. In this embodiment, a silver paste which is a low-resistivity material, or an alloy paste in which a small amount of palladium is mixed with silver is used as the conductor pattern. In addition, a paste of silver-palladium alloy is used for the heating element 620 so as to have a desired resistance value. Further, the heating element 620 and the conductor pattern are covered with an insulating coating layer made of heat resistant glass, and are electrically protected so as to prevent leakage and short circuit.

As shown in FIG. 1, electrodes 641, 651, 661, electrically connected to the power source (power source portion for supplying power to the heater) 110 and the connectors 700 (a, b) to both ends of the substrate 610 in the longitudinal direction. 671 is provided. Further, the substrate 610 is provided with a heating element 620 and branch paths 642(a-j).652(a-c).662(a-d).672(a,b) which are conductors. The branch path includes the common conductor path 640, the first opposing conductor path 650, the second opposing conductor path 660a, the third opposing conductor path 660b, the fourth opposing conductor path 670a, the fifth opposing conductor path 670b, and the heating element 620. It is a conductor path that is electrically connected.

In this embodiment, the heating elements 620(a to r) are formed on the substrate 610 as one elongated heating element along the length of the substrate. The heating element 620 of this embodiment has a width (length in the lateral direction) of about 1.5 to 2.0 mm, a thickness of about 20 μm, and a length of about 320 mm in the longitudinal direction. This length of about 320 mm is a length with which the entire area of the large size recording material P of A4 size (width size 297 mm) can be heated. The total resistance of the heating element 620 is about 10Ω.

The ten common branch paths 642a to 642j of the common conductor path 640 are stacked on the heating element 620 at intervals in the longitudinal direction, so that the heating element 620 is divided into nine sections by the common branch paths 642a to 642j. Separated into. The length of each section of the heating element 620 divided by the ten common branch paths 642a to 642j is about 35.6 mm. Further, a total of nine opposing branch paths 652(a-c), 662(a-d), 672(a,b) are laminated in the central portion of each section, and the heating element 620 has 18 of 620a to 620r. It is divided into individual sections. The length of each of the 18 sections is about 17.8 mm.

The common branch path 642(a-j) and the opposite branch paths 652(a-c).662(a-d).672(a,b) are provided so as to be orthogonal to the heating element 620.

The resistance values of the common branch path 642(a-j) and the counter branch paths 652(a-c).662(a-d).672(a,b) are significantly smaller than the resistance value of the heating element 620. Therefore, since the branch passages hardly generate heat, when the width of the branch passages (length in the longitudinal direction) becomes large, the heating element 620 has uneven heat generation. As a result, a temperature drop occurs in the branch path, and the gloss of the image on the recording material becomes uneven. This phenomenon is caused by the fact that the temperature of the belt 603 facing the branch path becomes low and the toner on the recording material cannot be sufficiently heated and melted, resulting in a low gloss.

The common branch path 642 (a to j) is electrically connected to the terminal 110a on one side of the power supply (power supply unit) 110 via the common conductor path 640, the common electrode 641, the connector 700a, and the like. Opposite branch paths 652(a-c), 662(a-d), 672(a,b) respectively include first to fifth opposed conductor paths 650, 660, 670, individual electrodes 651, 661, 671, It is electrically connected to the terminal 110b on the other side of the power source 110 via the connector 700b and the like.

That is, the common branch paths 642(a-j) and the opposite branch paths 652(a-c).662(a-d).672(a,b) are alternately arranged in the longitudinal direction of the heating element 620. The common conductor path 640 is formed along the longitudinal direction of the substrate 610, is connected to each common branch path 642 (a to j), and has one end connected to the common electrode 641.

Similarly, the first opposing conductor path 650, the second opposing conductor path 660a, the third opposing conductor path 660b, the fourth opposing conductor path 670a, and the fifth opposing conductor path 670b are formed along the longitudinal direction of the substrate 610. .. The first counter conductor path 650 is connected to the counter branch path 652 (a to c), and one end thereof is connected to the individual electrode 651. Further, the second and third opposing conductor paths 660a and 660b are respectively connected to the opposing branch paths 662(a to d), and one end thereof is connected to the individual electrode 661. The fourth and fifth opposing conductor paths 670(a,b) are connected to the opposing branch paths 672(a,b), respectively, and one end thereof is connected to the individual electrode 671.

As described above, the heating element 620 of the heater 600 of this embodiment is electrically connected to the power source 110 via the connector, the electrodes, the common conductor path, the opposing conductor path, and the branch path.

[Power supply to the heater]
Power is supplied to the heater 600 so that the small section heating elements in the portion corresponding to the width of the area corresponding to the width size of the recording material P heated with respect to the plurality of small section heating elements 620a to 620r generate heat. Done This is done by applying a voltage between the common electrode 641 and at least one of the plurality of individual electrodes 651, 661, 671. That is, a plurality of heat generation widths corresponding to the width size of the recording material P that heats the heat generation areas of the heat generating elements 620 (ar), a large heat generation width A, a medium heat generation width B, and a small heat generation in this embodiment. It is possible to change to three heating widths of width C.

This power feeding method will be described with reference to FIG. The power supply (power supply unit) 110 is a power supply circuit for the heater 600. In the present embodiment, a commercial AC power supply having an effective value of single-phase AC of about 100 V is used, and is equipped with a power supply terminal 110a and a power supply terminal 110b. The power supply 110 may be a DC power supply as long as it has a function of supplying electric power to the heater 600.

The control circuit 100 is electrically connected to the switches (SW) 643, 653, 663, and 673 for controlling the switches. The switch 643 is a switch (relay) provided between the power supply terminal 110a and the common electrode 641, and determines whether to connect the power supply terminal 110a and the common electrode 641 (on or off) according to an instruction from the control circuit 100. Switch.

The switch 653 is a switch provided between the power supply terminal 110b and the individual electrode 651, and switches whether to connect the power supply terminal 110b and the individual electrode 651 according to an instruction from the control circuit 100.

The switch 663 is a switch provided between the power supply terminal 110b and the individual electrode 661, and switches whether to connect the power supply terminal 110b and the individual electrode 661 according to an instruction from the control circuit 100.

The switch 673 is a switch provided between the power supply terminal 110b and the individual electrode 671, and switches whether to connect the power supply terminal 110b and the individual electrode 671 according to an instruction from the control circuit 100.

The control circuit 100 acquires the width size information of the recording material P in response to the reception of the print job (print job) execution instruction, and turns on/off the switches 643, 653, 663, and 673 according to the width size information. Control. That is, the control circuit 100 sets the heating area in the longitudinal direction of the heating element 620 (ar) to a heating width suitable for fixing the recording material P having the width size corresponding to the acquired width size information. Control. In the printer 1 of the present embodiment, since the recording material is conveyed on the basis of the center of the recording width, the above-described heat generation width change control of the heat generating element 620 (a to r) is also performed in the longitudinal direction of the heat generating element 620 (a to r). Performed on a central, central basis.

A method of changing the heat generation width of the heat generating element 620 (a to r) according to the widthwise size of the recording material P will be specifically described. First, when the recording material P has a large size such as an A4 lateral size (width size 297 mm), the control circuit 100 controls the heating element 620 to generate heat within the heating width A range. In this embodiment, the entire length area of the small section heating elements 620a to 620r corresponds to the width of the recording material having the maximum width size that can be used in the apparatus.

Specifically, the control circuit 100 turns on all the switches 643, 653, 663, and 673. In this case, a voltage is applied to the heater 600 between the common electrode 641 and all three individual electrodes 651, 661 and 671. As a result, in the heating element 620, all of the 18 small section heating elements 620a to 620r generate heat. At this time, the heater 600 generates heat in the entire length area of the heating element 620 of about 320 mm, and thus is in a heat generation state suitable for performing the fixing process of the recording material P of A4 lateral size.

When the recording material P has a medium size such as A4 vertical size (A4R size: width size 210 mm), the control circuit 100 controls the heating element 620 to generate heat in the heating width B range. Specifically, the control circuit 100 turns on the switches 643, 653, and 663 and turns off the switch 673.

In this case, a voltage is applied to the heater 600 between the common electrode 641 and the two individual electrodes 651 and 661. As a result, in the heating element 620, 14 sections of the small sections 620c to 620p out of the 18 small sections 620a to 620r generate heat. At this time, the heater 600 generates heat in an area of about 249 mm, which is a heat generation state suitable for performing the fixing process of the recording material P of A4 vertical size. Therefore, even when the fixing process of the recording material such as the A4 vertical size is performed, the small section heating elements 620a, 620b, 620q, and 620r corresponding to the portion where the recording material does not pass do not generate heat, and wasteful power is consumed. Never used.

When the recording material P has a small size such as a postcard size (100 mm in the width direction), the control circuit 100 controls the heating element 620 to generate heat in the heating width C range. Specifically, the control circuit 100 turns on the switches 643 and 653 and turns off the switches 663 and 673.

In this case, a voltage is applied to the heater 600 between the common electrode 641 and one individual electrode 651. As a result, the heating element 620 generates heat in the six small sections 620g to 620l of the eighteen small sections 620a to 620r. At this time, since the heater 600 generates heat in the area of about 107 mm, the heater 600 is in a heat generation state suitable for fixing the recording material P of the postcard size. Therefore, even when the recording material having a small size in the width direction such as the postcard size is fixed, the small section heating elements 620a to 620f and 620m to 620r corresponding to the portions where the recording material does not pass do not generate heat. , No use of wasted power.

[Heater temperature control]
In FIG. 1, 630k is a thermistor as a temperature sensor for heater temperature adjustment that raises and maintains the temperature of the heater portion within a width of the region width corresponding to the width size of the recording material P to be heated to a predetermined temperature. In the printer 1 of this embodiment, the recording material P is conveyed with the center as a reference. Therefore, the temperature control thermistor (temperature sensor for temperature control) 630k is provided on the back surface of the heater (heater area portion through which a recording material of any size is passed) corresponding to the longitudinal center of the heating element 620(a to r) of the heater 600. It is arranged in contact with the insulating coat layer portion.

The temperature control thermistor 630k is connected to the control circuit 100 via an A/D converter (not shown), and sends an output according to the detected temperature to the control circuit 100. The control circuit 100 is a circuit including a CPU that performs calculations associated with various controls and a non-volatile storage medium such as a ROM. A program is stored in the ROM, and various controls are executed by the CPU reading and executing the program. The control circuit 100 is electrically connected to the power supply 110 so as to control the energization of the power supply 110.

Further, the control circuit 100 reflects the temperature information acquired (input) from the temperature control thermistor 630k on the energization control of the power supply 110. That is, the control circuit 100 controls the electric power supplied to the heater 600 based on the output of the temperature control thermistor 630k. In the present embodiment, a method of adjusting the heat generation amount of the heater 600 by performing wave number control or phase control on the output of the power supply 110 is used, and when fixing the toner on the recording material, the heater 600 sets a predetermined amount. Raised to temperature and maintained.

630a, 630c, 630e, 630f, 630h, and 630j are the temperatures arranged in contact with the insulating coat portion on the back surface of the heater to detect the temperature of each width end of the plurality of heat generation widths A, B, and C of the heater 600. An end thermistor (end temperature sensor) as a sensor. Although this end thermistor will be described later, these end thermistors are also connected to the control circuit 100 via an A/D converter (not shown) and transmit an output according to the detected temperature to the control circuit 100.

The temperature control thermistor 630k has higher detection resolution than the end thermistors 630a, 630c, 630e, 630f, 630h, and 630j. In the present embodiment, the size of the temperature control thermistor 630k is approximately 5 [mm] horizontally and approximately 2 [mm] vertically. The end thermistors 630a, 630c, 630e, 630f, 630h, and 630j are approximately 2 mm in length and width. That is, the temperature control thermistor 630k and the end part thermistors 630a, 630c, 630e, 630f, 630h, and 630j are different types.

[Characteristic Configuration of Example Heater]
The heater 600 of this embodiment is characterized in that the end thermistor 630a serving as a temperature sensor is provided in contact with the back surface of the heater in order to detect the temperature of each end of each of the plurality of heat generation widths A, B, and C. -It has 630c*630e*630f*630h*630j. That is, by providing the end temperature sensors 630a, 630c, 630e, 630f, 630h, 630j for detecting the temperature of the heater portion corresponding to the respective width end portions of the plurality of heat generation widths A, B, C. is there.

As described above, according to the width size of the recording material P to be heated with respect to the plurality of small section heat generating elements 620a to 620r, the electrodes 641 and 651 are arranged so that the small section heating elements in the portion corresponding to the area width corresponding to the width size generate heat. -A voltage is selectively applied to 661 and 671. The end thermistors 630a, 630c, 630e, 630f, 630h, and 630j detect the temperature of the heater portion corresponding to the outer end of the region width of the small section heating element located at the end of the region width.

In the heater 600 of this embodiment, the total length of the heating element 620 divided into the plurality of small section heating elements 620a to 620r is 320 mm. When the recording material to be heated is the A4 size (width size 297 mm) which is a large size recording material, all the small section heating elements 620a to 620r are caused to generate heat. That is, the heat generation width A is 320 mm, and the area width corresponding to the width size of A4 size is 297 mm. Therefore, width portions of about 11.5 mm on both ends of the heat generation width A are non-passing portions of the recording material, which are so-called non-passing portion temperature rises (non-sheet passing portion temperature rises).

Therefore, the end thermistors 630a and 630j are arranged so as to detect the temperature of the heater portion corresponding to the outer end of the region width 297 mm in the small section heating elements 620a and 620r corresponding to the end of the region width 297 mm. There is.

When the recording material to be heated is an A4R size (width size 210 mm) which is a medium-sized recording material, the small section heating elements 620c to 620p are caused to generate heat. That is, the heat generation width B is about 249 mm, and the area width corresponding to the width size of A4R size is 210 mm. Therefore, the width portions of about 20 mm on both ends of the heat generation width B are the recording material non-passing portions, and the non-passing portions can be heated.

Therefore, the end thermistors 630c and 630h are arranged so as to detect the temperature of the heater portion corresponding to the outer end of the region width 210mm in the small section heating elements 620c and 620p located corresponding to the end of the region width 210mm. There is.

Further, when the recording material to be heated is a postcard size (width size 100 mm) which is a small size recording material, the small section heating elements 620g to 620l are caused to generate heat. That is, the heat generation width C is about 107 mm, and the region width corresponding to the postcard size width size is 100 mm. Therefore, the width portions of about 3.5 mm on both end sides of the heat generation width C are the recording material non-passing portions, and the non-passing portions can be heated.

Therefore, the end thermistors 630e and 630f are arranged so as to detect the temperature of the heater portion corresponding to the outer end of the region width 100mm in the small section heating elements 620g and 620l located corresponding to the end of the region width 100mm. There is.

These end thermistors 630a, 630c, 630e, 630f, 630h, and 630j are also connected to the control circuit 100 via an A/D converter (not shown), and transmit an output according to the detected temperature to the control circuit 100.

By doing so, the temperature of the recording material non-passing portion (non-passing portion area) in each of the heat generation widths A, B, and C (non-passing portion heating temperature) can be detected, and the belt 603 can be prevented from becoming high temperature. The life of the belt 603 can be prevented from being shortened. The cause of shortening the life of the belt 603 is that the adhesive between the base material 603a of the belt 603 and the elastic layer 603b is thermally deteriorated and the elastic layer 603b is peeled off from the base material 603a.

In this embodiment, the belt surface temperature is controlled to be 230[° C.] or lower. Specifically, when the belt surface temperature exceeds 230[° C.], the energization control of the heater 600 is changed or the productivity is lowered so that the non-passage temperature of the recording material does not exceed 230[° C.]. Have control.

For example, as shown in FIG. 3, when the recording material P of A4R (vertical) size is used, in the non-passage portion E which is the difference between the width of the recording material and the heat generation width B of the heater 600, the heat of the heater 600 is Is not lost to the recording material, and the temperature rises easily.

By arranging the end thermistors 630c and 630h at the locations shown in FIG. 3, the controller 100 can detect an abnormal temperature rise in the recording material non-passing portion E of the heater 600. Based on the detected temperature information input from the end thermistors 630c and 630h, the control unit 100 changes the energization control of the heater 600 so that the temperature of the recording material non-passing portion E does not exceed a predetermined temperature, or Controlling a drop in productivity. As a result, it is possible to prevent the life of the belt 603 from being shortened due to the abnormal temperature rise in the recording material non-passing portion E.

In this embodiment, the end thermistors 630a, 630c, 630e, 630f, 630h, and 630j are arranged as shown in FIG. 1 in consideration of the case of using a recording material having another width size.

The heater 600 of the present embodiment has only three heat generation widths A, B, and C, but is not limited to this structure and has four or more heat generation widths. It goes without saying that it can be applied to the configuration.

As described above, the heater 600 according to the present embodiment can change the heat generation width of the heating elements 620 (a to r) according to the width size of the recording material P to be heated, and the abnormal temperature rise of the heater 600 can be achieved. It is possible to provide a fixing device that can prevent such a problem.

<<Example 2>>
A fixing device according to the present exemplary embodiment and an image forming apparatus including the fixing device will be described. Since the configuration of the image forming apparatus is the same as that of the first embodiment shown in FIG. 5, the description thereof is omitted, and only the configuration of the fixing device will be described here. Also in the fixing device, the description of the same parts as those in the first embodiment will be omitted.

The second embodiment is an embodiment in which a failure of the thermistor is considered in addition to the heater configuration of the first embodiment. With this configuration, even if the thermistor fails, the abnormal temperature rise of the heater 600 can be reliably detected.

The heater configuration of the second embodiment is shown in FIG. In the configuration shown in FIG. 8, the end thermistors 630a, 630c, 630e, 630f, 630h, and 630 are arranged at the end of the subdivision heating element of the various heating widths A, B, and C, as in the first embodiment. To do. Then, another end outer thermistor (outer end temperature sensor) 630b, 630d, 630g, 630i is arranged adjacent to each of the arranged end thermistors.

The outer end thermistors 630b, 630d, 630g, and 630i control the temperature of the heater portion adjacent to the end thermistor outside the small section heating element located at the end of the area width corresponding to the width size of the recording material to be heated. Detect. In the present embodiment, the outside temperature sensors 630b, 630d, 630g, 630i are heater portions corresponding to the inner ends of the small section heating elements adjacent to the outside of the small section heating elements located at the ends of the area width. Detects the temperature of.

That is, in addition to the configuration of the first embodiment, the outer end thermistors 630b, 630d, 630g, 630i are added. These outer end thermistors 630b, 630d, 630g, and 630i are also connected to the control circuit 100 via an A/D converter (not shown) and transmit an output according to the detected temperature to the control circuit 100. The size of the outer end thermistors 630b, 630d, 630g, and 630i is about 2 mm in both length and width, similarly to the end thermistors 630a, 630c, 630e, 630f, 630h, and 630.

FIG. 9 shows an example of detecting an abnormal temperature rise of the heater 600. Since FIG. 9 shows an example in which an A4R size recording material is used, energization control is performed on the small section heating elements 620c to 620p so that the heating element 620 generates heat (lights) up to the heating width B.

FIG. 9 shows an example in which a part of the common conductor path 640 (the portion of the abnormal portion 1) is broken. When the abnormal portion 1 is disconnected, the heater 600 generates heat only in the heat generation range D of the heat generation width B. In that state, if the end part thermistor 630c fails, the high temperature part (the recording material non-passing part E) of the heater 600 cannot be detected. Therefore, in this embodiment, by disposing the outer end thermistor 630b adjacent to the end thermistor 630c, it is possible to suppress the temperature rise of the heater 600 before the temperature at which the belt 603 becomes abnormal.

FIG. 10 shows a graph of temperature changes of the end thermistor 630c and the outer end thermistor 630b with respect to time. As shown in FIG. 10, when the end thermistor 630c reaches 270° C., the outer end thermistor 630b detects 250° C. The temperature at which the abnormality occurs in the belt 603 is 270° C., so the control circuit 100 energizes the heater 600 so that the high temperature part of the heater does not exceed 270° C. when the outer end thermistor 630 b detects the temperature of 250° C. Change control. As a result, the high temperature portion of the heater 600 does not exceed 270° C., and the belt 603 does not have a short life.

Considering the use of recording materials of other failure modes and other widths, the outer edge thermistors 630b, 630d, 630g and 630i shown in FIGS. 8 and 9 are added.

Although the end thermistor and the outer end thermistor are arranged adjacent to each other in the longitudinal direction of the heating element 620 in the second embodiment, they may be arranged adjacent to each other in the lateral direction.

In the heater 600 of the embodiment, the changeable width of the heat generating area of the heat generating element 620 is set to three widths of a large heat generating width A, a medium heat generating width B, and a small heat generating width C. However, it is needless to say that the present invention is not limited to this structure, and can be applied to a structure having four or more heating regions.

As described above, the heater 600 according to the present embodiment can change the heat generation width of the heating elements 620 (a to r) according to the width size of the recording material to be heated, and the abnormal temperature rise of the heater 600 can be achieved. Suppression can be prevented. Further, a fixing device using this heater 600 can be provided.

<<Other Examples>>
(1) The numerical values such as the dimensions illustrated in the embodiments are examples, and the present invention is not limited to these numerical values. Numerical values can be appropriately selected within a range in which the present invention can be applied. Further, the configurations described in the embodiments may be appropriately changed within the scope of the present invention.

(2) The control for changing the width of the heat generation area of the heater 600 is not limited to the central reference. When the recording material is conveyed on the one side basis, the control for changing the width of the heat generation width is based on the end portion.

(3) In the heater 600 of the embodiment, a plurality of common branch paths and a plurality of opposed branch paths are alternately stacked on the heating element 620 extending along the longitudinal direction of the substrate 610 to generate heat in a plurality of small sections. It is divided into bodies 620a to 620l. A configuration is provided in which a plurality of common branch paths and a plurality of opposed branch paths are alternately arranged along the longitudinal direction of the substrate 610 at intervals and the heating elements 620a to 620l are formed between adjacent branch paths. Good.

(4) The number of electrodes 641, 651, 661 and 671 is not limited to four in the heater 600 of the embodiment. A heater configuration having three or five or more heaters can also be used. The plurality of electrodes are not limited to the configuration in which the plurality of electrodes are separately located on one end side and the other end side in the longitudinal direction of the substrate 610 like the heater 600 of the embodiment. Alternatively, all the electrodes may be located on one end side or the other end side of the substrate 610 in the longitudinal direction.

(5) The belt 603 is not limited to the structure in which the inner surface of the belt 603 is supported by the heater 600 and is driven by the roller 70. For example, a belt unit system may be used in which the belt unit system spans a plurality of rollers and is driven by any one of the plurality of rollers.

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

(7) The fixing device is not limited to use as a device that heats and fixes an unfixed toner image formed on a recording material as a fixed image. It is also effective as a device for adjusting the surface texture of an image such as improving the glossiness of the image by re-heating and pressing the toner image once fixed or supposedly attached to the recording material. Device called).

(8) The image forming apparatus is not limited to the image forming apparatus that forms a full-color image as in the embodiment, but may be an image forming apparatus that forms a monochrome image. Further, the image forming apparatus can be implemented in various applications such as a copying machine, a FAX, and a multi-functional machine having a plurality of these functions in addition to necessary equipment, equipment, and housing structure.

40..Fusing device, 600..Heater, 610..Substrate,.. Resistance heating element, 620a to 620r..Small section heating element, 641, 651, 661, 671.., electrode, 640, 650, 660, 670 ..Conductor path, 642.652.662.672..Branch path, 630a.630c.630e.630f.630h.630j..End temperature sensor, 630b.630d.630g.630i.. 630k・・Temperature sensor for temperature control, 100・・Control unit, 110・・Power supply unit

Claims (8)

A heater used for a fixing device that heats an image on a recording material,
An elongated substrate,
A resistance heating element that generates heat by energization extending along the length of the substrate;
A plurality of electrodes provided on the substrate,
A plurality of conductor tracks extending from each of the plurality of electrodes,
A plurality of branch paths branching from each of the plurality of conductor paths at intervals along the longitudinal direction, the branch paths being electrically connected to the resistance heating element across the resistance heating element; in anda branch passage the resistance heating element along the longitudinal are divided into a plurality of small sections heating unit,
In heater the selective voltage to the plurality of electrodes is applied to small section heating unit that written in a region width corresponding to the width size is heat according to the width size of the recording material conveyed,
Within the region of the small-section heat generating portion corresponding to the end of the region width, the small-region heat generation provided outside the region width in the longitudinal direction of the resistance heating element and corresponding to the end of the region width. An end temperature sensor for detecting the temperature of a section, and a small section heat generating element outside the small section heating section corresponding to the end portion of the region width in the longitudinal direction of the resistance heating element and corresponding to the end portion of the region width. An end outside temperature sensor for detecting the temperature of the small section heat generating portion adjacent to the section,
The outside-end temperature sensor detects the temperature of the inside end in the longitudinal direction of the resistance heating element in the region of the small-section heat generating part adjacent to the small-section heat generating part corresponding to the end of the region width. Heater. The heater according to claim 1 , wherein a temperature sensor for temperature control is arranged to control the temperature of the heater portion in the area width to a predetermined temperature. Wherein said end portion temperature sensor and the temperature sensor temperature control is Ri types Do different, heater according to claim 2 wherein the temperature sensor temperature control is characterized in that higher detection resolution than said end portion temperature sensor. The heater according to any one of claims 1 to 3 , wherein the entire length areas of the plurality of small section heat generating portions correspond to the width size of the recording material having the maximum width that can be used. A heater according to any one of claims 1 to 4 ,
An endless belt that moves while sliding in contact with the heater,
A pressing member that abuts against the heater while sandwiching the endless belt ,
A fixing device characterized in that a recording material is nipped and conveyed at a nip portion formed between the endless belt and the pressure member to heat an image on the recording material. A power supply unit for supplying power to the heater, and a control unit for controlling power supply from the power supply unit to the heater, the control unit according to a width size of a recording material to be heated with respect to the plurality of small section heat generating units. the fixing device according to claim 5, characterized in that the voltage is selectively applied to the plurality of electrodes as small section heating unit generates heat in the part relating to the region width corresponding to the width size Te. 7. The fixing device according to claim 6 , wherein the controller applies a voltage to all of the plurality of electrodes when the recording material having the maximum width size usable in the apparatus is heated. A temperature control temperature sensor for controlling the temperature of the heater portion in the region width to a predetermined temperature is arranged, and the control unit controls the heater in the region width based on the detected temperature information input from the temperature control temperature sensor. 8. The fixing device according to claim 6 , wherein electric power supplied from the power supply unit to the heater is controlled so that the temperature of the portion is maintained at a predetermined temperature.