JP2013186402A - Fixation device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixation device capable of creating an image without exceeding a heat resistant temperature of an isolation layer of a planar heating element, and to provide an image formation apparatus having the fixation device.SOLUTION: A fixation device includes: a fixation member; a pressure member; a contact member for making contact with the pressure member through the fixation member to form a nip part; a planar heating element; a heater element supporting member for supporting the planar heating element; first temperature detection means for detecting a surface temperature of the planar heating element; second temperature detection means for detecting an outer peripheral surface temperature of the fixation member; tension fluctuation means for applying a pressure onto the fixation member from an inner peripheral side of the fixation member to fluctuate a tension of the fixation member; and a controlling unit for activating the tension fluctuation means according to the temperature detected at the first temperature detection means and the temperature detected at the second temperature detection means to adjust the tension of the fixation member.

Description

  The present invention relates to a fixing device and an image forming apparatus.

  Conventionally, various image forming apparatuses using an electrophotographic system have been devised as image forming apparatuses such as copying machines and printers, and are well known in the art. In the image forming process, an electrostatic latent image is formed on the surface of the photosensitive drum as an image carrier, and the electrostatic latent image on the photosensitive drum is developed with a toner as a developer to be visualized and developed. This process is established by a process in which the transferred image is transferred onto a recording paper by a transfer device to carry the image, and the toner image on the recording paper is fixed by a fixing device using pressure or heat.

  In this fixing device, a fixing member and a pressure member constituted by opposing rollers or belts or a combination thereof are arranged so as to contact each other to form a nip portion, and a recording sheet is sandwiched in the nip portion, Heat and pressure are applied to fix the toner image on the recording paper.

  As an example of a fixing device, a technique using a fixing belt stretched around a plurality of roller members as a fixing member is known as in Patent Document 1. An apparatus using such a fixing belt is provided in a fixing belt (endless belt) as a fixing member, a plurality of roller members that stretch and support the fixing belt, and one of the plurality of roller members. And a heater, a pressure roller (pressure member), and the like. The heater heats the fixing belt via the roller member. Then, the toner image on the recording medium conveyed toward the nip formed between the fixing belt and the pressure roller is fixed on the recording medium by receiving heat and pressure at the nip. Belt fixing method).

  Further, in the fixing device used in the image forming apparatus described above, there is a fixing device having a fixing member that is in sliding contact with the inner surface of a fixing member that is a rotating body.

  For example, in Patent Document 2, a fixing nip portion is formed by sandwiching a heat resistant film (fixing film) between a ceramic heater as a heating element and a pressure roller as a pressure member, and a film in the fixing nip portion. The recording material on which an unfixed toner image to be image-fixed is formed and carried is introduced between the pressure roller and the pressure roller, and is nipped and conveyed together with the film, so that the heat of the ceramic heater passes through the film at the nip portion. A film heating type fixing device is disclosed in which an unfixed toner image is fixed to a surface of a recording material by applying pressure at a fixing nip portion. This film heating type fixing device can be configured as an on-demand type device using a ceramic heater and a member having a low heat capacity as a film, and energizes the ceramic heater as a heat source only when the image forming apparatus performs image formation. Thus, it is only necessary to generate heat at a predetermined fixing temperature, the waiting time from the power-on of the image forming apparatus to the image forming executable state is short (quick start property), and the power consumption during standby is greatly reduced ( There are advantages such as (power saving).

  In Patent Documents 3 and 4, a rotatable heat-fixing roll whose surface is elastically deformed, an endless belt (pressure belt) that can run while being in contact with the heat-fixing roll, and a non-rotating state inside the endless belt And a pressure pad that elastically deforms the surface of the heat-fixing roll, and is provided with a belt nip through which the recording paper can pass between the endless belt and the heat-fixing roll. A pressure belt type image fixing device is proposed. According to this fixing method, the lower pressure member is used as a belt, and the contact area between the paper and the roll is widened to greatly improve the heat conduction efficiency, and it is possible to reduce the energy consumption and at the same time realize the miniaturization. It has become.

  However, although the fixing device described in Patent Document 1 described above is suitable for speeding up the device as compared with a device using a fixing roller, the warm-up time (time required to reach a printable temperature) and the first print There is a limit to shortening the time (the time from when a print request is received to when the print operation is performed and the paper discharge is completed).

On the other hand, the fixing device described in Patent Document 2 can reduce the warm-up time and the first print time by reducing the heat capacity, and also reduce the size of the device. However, the fixing device described in Patent Document 2 has a problem of durability and a problem of belt temperature stability. In other words, the wear resistance due to the sliding between the ceramic heater, which is a heat source, and the inner surface of the belt is insufficient. Or, a phenomenon such as an increase in the driving torque of the fixing device occurs, and as a result, the transfer paper forming the image slips and the image shifts, or the stress on the driving gear increases, causing damage to the gear. (Problem 1).
In the film heating type fixing device, since the belt is locally heated at the nip portion, when the rotating belt returns to the nip entrance, the belt temperature becomes the coldest state (especially at high speed rotation). , There was a problem that fixing failure was likely to occur (Problem 2).

  On the other hand, in Patent Document 3, a glass fiber sheet (PTFE-impregnated glass cloth) impregnated with PTFE as a low friction sheet (sheet-like sliding material) on the surface layer of the pressure pad is used, and the slidability of the belt inner surface and the fixing member is improved. Means for improving the problem are disclosed. However, such a pressure belt type fixing device (Patent Documents 3 and 4) has a problem in that it takes a long time to warm up because the heat capacity of the fixing roller is large and the temperature rise is slow. (Problem 3).

  With respect to the above problems 1 to 3, in Patent Documents 5 and 6, a substantially pipe-shaped counter member (metal heat conductor) disposed on the inner peripheral side of the endless fixing belt, By providing a resistance heating element such as a ceramic heater that is arranged on the peripheral side and heats the opposing member, the entire fixing belt can be warmed, the warm-up time and first print time can be shortened, and high speed There has been proposed a fixing device that can solve the shortage of heat during rotation. However, this method is not sufficient in terms of shortening the warm-up time and the first print time because the heat of the resistance heating element is transmitted to the fixing belt through the opposing member (metal heat conductor).

  On the other hand, in Patent Document 7, an endless fixing belt, a pressure roller that presses against the fixing belt to form a nip portion on which a recording medium is conveyed, and an inner peripheral surface of the fixing belt are fixed. There has been proposed a fixing device that includes a resistance heating element that heats the fixing belt, and the resistance heating element is arranged with a small gap so as not to be in pressure contact with the inner peripheral surface of the fixing belt. As a result, even when the warm-up time and the first print time are shortened and the apparatus is speeded up, it is possible to prevent problems such as defective fixing and wear and damage of the fixing member and the resistance heating element. It is supposed to be.

  Further, in Patent Document 8, a fixing member of a rotating endless belt, a pressure member in contact with the outer peripheral surface of the fixing member, and an inner peripheral side of the fixing member are arranged to contact the pressure member via the fixing member. A contact member that forms a nip portion in contact with the sheet, a sheet heating element that is disposed in contact with or close to the fixing member on the inner peripheral side of the fixing member, and directly or indirectly heats the fixing member; and a fixing member And a heating element support member that is disposed so as to sandwich a sheet heating element between the fixing member and an inner peripheral side of the sheet heating member and supports the sheet heating element at a predetermined position. . Here, the planar heating element is formed of a resistance heating layer in which conductive particles are dispersed in a heat-resistant resin and an electrode layer for supplying power to the resistance heating layer on an insulating base layer. The heat generating sheet has a predetermined width and length corresponding to the axial direction and the circumferential direction of the fixing member and exhibits flexibility. This has the following effects.

  Since the heat capacity of the fixing member and the sheet heating element is small, it is possible to shorten the warm-up time and the first print time while suppressing energy consumption. In addition, since the heat generating sheet in the sheet heating element is a resin-based sheet, the stress caused by the rotation and vibration of the pressurizing member repeatedly acts on the heat generating sheet, and even if the heat generating sheet is repeatedly bent, fatigue failure occurs. It is possible to operate for a long time.

  By providing the above fixing device in the image forming apparatus, the warm-up time and the first print time are short, and even if the size of the recording medium is changed, it is possible to form an appropriate image while suppressing the energy consumption, and the speed of the apparatus is increased. Even in this case, it is possible to prevent problems such as fixing failure.

However, in the configuration as in Patent Document 8, when the temperature of the heat generating portion of the planar heating element is high (when the output per unit area (W / cm ² ) of the planar heating element is large), the planar heating element is used. Since there is an insulating layer between the heat generating portion of the heat generating element and the fixing member, a temperature difference occurs between the planar heat generating element and the fixing member. At this time, if the lighting of the planar heating element is controlled only by the surface temperature of the fixing member, the temperature of the insulating layer of the planar heating element rises and the temperature of the insulating layer becomes higher than the heat resistant temperature. there were.
SUMMARY An advantage of some aspects of the invention is that it provides a fixing device that does not exceed the heat resistance temperature of an insulating layer of a planar heating element and an image forming apparatus including the fixing device. .

  In order to solve the above-mentioned problems, in the present invention, a fixing member of a rotating endless belt, a pressure member in contact with the outer peripheral surface of the fixing member, and an inner peripheral side of the fixing member, the fixing member A contact member that forms a nip portion by contacting with the pressure member via a fixing member, and is disposed in contact with or close to the fixing member on the inner peripheral side of the fixing member, so that the fixing member is directly or indirectly disposed And a heating element disposed on the inner peripheral side of the fixing member so as to sandwich the planar heating element between the fixing member and supporting the planar heating element at a predetermined position. A first temperature detection means disposed between a support member, the planar heating element and the heating element support member for detecting a surface temperature of the planar heating element; and It is arranged at a position opposite to the fixing member, and the outer peripheral surface temperature of the fixing member is measured. Second temperature detecting means for performing the above, a tension changing means for changing the tension of the fixing member by applying a pressing force to the fixing member from the inner peripheral side of the fixing member, and a temperature detected by the first temperature detecting means. And a control unit that adjusts the tension of the fixing member by operating the tension fluctuation unit based on the temperature detected by the second temperature detection unit.

  According to the present invention, a fixing device capable of forming an image without exceeding the heat resistance temperature of the insulating layer of the planar heating element and an image forming apparatus including the fixing device are realized.

FIG. 3 is a schematic cross-sectional view illustrating a configuration of the fixing device according to the first embodiment. 2A and 2B are schematic diagrams illustrating a configuration of a fixing member in the fixing device, in which FIG. 2A is a schematic perspective view of the fixing member, and FIG. 2B is a schematic cross-sectional view of the fixing member. It is a cross-sectional schematic diagram of the basic composition of the heat_generation | fever sheet | seat in a planar heating element. It is a figure explaining the assembly of a fixing member. It is a figure explaining the assembly of a fixing member. It is a figure explaining the assembly of a fixing member. It is a schematic diagram of tension variation means. It is a flowchart explaining control of pressing force. It is an upper surface schematic diagram which shows the structural example (1) of a planar heating element. It is an upper surface schematic diagram which shows the structural example (2) of a planar heating element. It is an upper surface schematic diagram which shows the structural example (3) of a planar heating element. It is a disassembled perspective view which shows the structural example (4) of a planar heating element. FIG. 6 is a schematic cross-sectional view illustrating an arrangement example of a rotation support member, a planar heating element, and a contact member in the fixing device. FIG. 6 is a schematic cross-sectional view illustrating a configuration of a fixing device according to a second embodiment. FIG. 6 is a schematic cross-sectional view illustrating a configuration of a fixing device according to a second embodiment. FIG. 6 is a schematic cross-sectional view illustrating a configuration of a fixing device according to a second embodiment. 1 is an overall configuration diagram illustrating a configuration of an image forming apparatus.

  Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the embodiments described below.

FIG. 1 is a schematic cross-sectional view illustrating the configuration of the fixing device according to the first embodiment.
2A and 2B are schematic diagrams illustrating a configuration of a fixing member in the fixing device, in which FIG. 2A is a schematic perspective view of the fixing member, and FIG. 2B is a schematic cross-sectional view of the fixing member.

  A fixing device 20 shown in FIG. 1 includes a fixing member 21 (also referred to as a fixing sleeve 21 or a fixing rotator 21) formed of a rotating endless belt, and a pressure member 31 (pressure roller) that contacts the outer peripheral surface of the fixing member 21. 31 or a pressure rotator 31), a contact member 26 that is disposed on the inner peripheral side of the fixing member 21 and contacts the pressure member 31 via the fixing member 21 to form a nip portion, and a fixing member A sheet heating element 22 that is disposed in contact with or close to the fixing member 21 on the inner peripheral side of the member 21 and heats the fixing member 21 directly or indirectly, and the fixing member 21 on the inner peripheral side of the fixing member 21. And a heating element support member 23 which is disposed so as to sandwich the planar heating element 22 therebetween and supports the planar heating element 22 at a predetermined position. FIG. 1 shows a configuration in which the planar heating element 22 abuts on the inner peripheral surface of the fixing member 21 and directly heats.

  The fixing device 20 is disposed between the planar heating element 22 and the heating element support member 23, and includes a first temperature detection unit 41 that detects the surface temperature of the planar heating element 22, and a first temperature detection unit 41. And a second temperature detecting means 42 for detecting the outer peripheral surface temperature of the fixing member 21 and a pressing force to the fixing member 21 from the inner peripheral side of the fixing member 21. And a tension varying means 55 that varies the tension of the fixing member 21 by applying the tension. The position in the circumferential direction of the tension varying means 55 shown in FIG. 1 is merely an example, and it may be arranged at any position other than the nip portion.

  Further, the fixing device 20 controls the tension of the fixing member 21 by operating the tension changing means 55 based on the temperature detected by the first temperature detecting means 41 and the temperature detected by the second temperature detecting means 42. The unit 45 is provided. In addition, although a temperature detection means is a thermistor, for example, it is not restricted to this. In addition, the first temperature detection unit 41 and the second temperature detection unit 42 are provided at positions facing each other in the example of FIG. 1, but there may be a predetermined shift in the circumferential direction of the fixing member 21. When there is a deviation, control considering the deviation may be performed.

  The planar heating element 22 is formed with a resistance heating layer in which conductive particles are dispersed in a heat-resistant resin and an electrode layer for supplying power to the resistance heating layer on an insulating base layer. A heat generating sheet having a predetermined width and length corresponding to the axial direction and the circumferential direction of the fixing member 21 and having flexibility is provided. The fixing device 20 uses the temperature of the tension generating unit 55 based on the temperature detected by the first temperature detecting unit 41 and the temperature difference between the temperature detected by the first temperature detecting unit 41 and the temperature detected by the second temperature detecting unit 42. The pressing force against the fixing member 21 is adjusted.

  The fixing member 21 is a flexible pipe-shaped endless belt having a length corresponding to the width of the recording medium P through which the axial direction passes, and has a thickness of, for example, 30 to 50 μm. At least a release layer is formed on a substrate made of the above, and the outer diameter is 30 mm. Hereinafter, as shown in FIG. 2A, the pipe longitudinal direction of the fixing member 21 is referred to as an axial direction, and as shown in FIG. 2B, the pipe circumferential direction of the fixing member 21 is referred to as a circumferential direction.

  As a material for forming the base material of the fixing member 21, a metal material having good heat conductivity such as iron, cobalt, nickel, or an alloy thereof can be used.

  The release layer of the fixing member 21 is obtained by coating a fluorine compound such as PFA in a tube shape, and the thickness thereof is 50 μm. The release layer is for enhancing the toner release property on the surface of the fixing member 21 with which the toner image (toner) T on the recording medium P is in direct contact.

  The pressure member 31 is formed by sequentially forming a heat-resistant elastic layer such as silicone rubber (solid rubber) and a release layer on a metal core made of a metal material such as aluminum or copper, and has an outer diameter of 30 mm. It has become. The elastic layer is formed to have a thickness of 2 mm. The release layer is coated with a PFA tube and is formed to have a thickness of 50 μm. Further, a heating element such as a halogen heater may be incorporated in the cored bar as necessary. The pressure member 31 is pressed against the contact member 26 via the fixing member 21 by a pressure means (not shown), and the pressure contact portion forms a nip portion 21n that is recessed on the fixing member 21 side. Then, the recording medium P is conveyed to the nip portion 21n.

  The pressure member 31 is rotationally driven by a driving mechanism (not shown) in a state where it is in pressure contact with the fixing member 21 (rotates in the clockwise direction in FIG. 1), and the fixing member 21 is rotated as the pressure member 31 rotates. It will rotate (rotating counterclockwise in FIG. 1).

  The contact member 26 has a length in the axial direction of the fixing member 21, and at least a portion in pressure contact with the pressure member 31 through the fixing member 21 is made of an elastic body having heat resistance such as fluorine rubber. In addition, the core holding member 28 is fixed in a state of being held at a predetermined position on the inner peripheral side of the fixing member 21. Further, the portion of the contact portion 26 that contacts the inner peripheral surface of the fixing member 21 is preferably made of a material having excellent sliding properties and wear resistance, such as a Teflon (registered trademark) sheet.

  The core holding member 28 is a rigid member having a length corresponding to the length in the axial direction of the fixing member 21 and having an H-shaped cross section. It is arranged at a substantially central portion on the circumferential side.

  The core holding member 28 holds various members arranged on the inner peripheral side of the fixing member 21 at predetermined positions. For example, one of the H-shaped core holding members 28 (opposite to the pressure member 31). The abutting member 26 is housed and held in a recessed portion on the side), and is supported from the side opposite to the nip portion 21n so that the abutting member 26 is not greatly deformed even when pressed by the pressure member 31. The core holding member 28 holds the abutting member 26 so as to slightly protrude from the core holding member 28 toward the pressure member 31. The core holding member 28 (or a heating pipe 27 to be described later) is formed at the nip portion 21n. ) Is arranged so as not to contact the fixing member 21.

  In addition, the other side of the H-shaped core holding member 28 (opposite to the pressing member 31 side) has a length corresponding to the axial length of the fixing member 21 and a T-shaped cross section. A terminal block stay 24 having a shape and a power supply line 25 that extends on the terminal block stay 24 and supplies electric power from the outside are housed and held. Further, the heating element support member 23 is held on the H-shaped outer surface of the core holding member 28. In FIG. 1, the heating element support member 23 is held in the region of the lower half of the fixing member 21 (the half of the nip portion on the entry side). At this time, the heating element support member 23 and the core holding member 28 may be bonded in consideration of assembly. Alternatively, in order to prevent heat transfer from the heating element support member 23 side to the core holding member 28 side, both may be non-bonded.

  The heating element support member 23 supports the planar heating element 22 in order to place the planar heating element 22 in contact with the inner peripheral surface of the fixing member 21 or close to the fixing member 21 with a predetermined gap. Therefore, the heating element support member 23 has an outer peripheral surface having a predetermined arc length along the inner peripheral surface of the fixing member 21 having a circular cross-sectional shape.

  Further, the heating element support member 23 has heat resistance sufficient to withstand the heat generation of the sheet heating element 22 and sheet heating without deformation when the rotating fixing member 21 contacts the adjacent sheet heating element 22. It is preferable to have strength sufficient to support the body 22 and heat insulation so that the heat of the sheet heating element 22 is not transmitted to the core holding member 28 side but to the fixing member 21 side, for example, polyimide resin. It is preferable. When the sheet heating element 22 is in contact with the inner peripheral surface of the fixing member 21, the force that the rotating fixing member 21 pulls the sheet heating element 22 toward the nip portion acts on the sheet heating element 22. For this reason, the heating element support member 23 needs to be strong enough to support the planar heating element 22 without being deformed. In this case, polyimide resin is preferable.

FIG. 3 is a schematic cross-sectional view of the basic configuration of the heat generating sheet in the planar heat generating element.
The planar heating element 22 includes a resistance heating layer 22b in which conductive particles are dispersed in a heat-resistant resin on an insulating base layer 22a, an electrode layer 22c that supplies power to the resistance heating layer 22b, And a heat generating sheet 22s having a predetermined width and length corresponding to the axial direction and the circumferential direction of the fixing member 21 and exhibiting flexibility. On the base layer 22a, an insulating layer 22d is provided that insulates between the resistance heating layer 22b and an electrode layer 22c of another power feeding system adjacent to the base layer 22a or between an edge portion of the heating sheet 22s and the outside. The planar heating element 22 is connected to the electrode layer 22c at the end of the heating sheet 22s, and an electrode terminal 22e (not shown in FIG. 3) that supplies power supplied from the power supply line 25 to the electrode layer 22c. Provided below.

  Further, the thickness of the heat generating sheet 22s is about 0.1 to 1 mm, and is flexible enough to be wound around at least the outer peripheral surface of the heat generating element support member 23.

  Here, the base layer 22a is a thin-film elastic film made of a resin having a certain degree of heat resistance such as PET or polyimide resin, and among these, a film member made of polyimide resin is preferable. Thereby, heat resistance, insulation, and a certain amount of flexibility (flexibility) are provided.

  The resistance heating layer 22b is a conductive thin film in which conductive particles such as carbon particles and metal particles are uniformly dispersed in a heat-resistant resin such as polyimide resin. It is configured to generate heat. Such a resistance heating layer 22b may be formed by applying a coating material in which conductive particles such as carbon particles and metal particles are dispersed in a precursor of a heat resistant resin such as polyimide resin on the base layer 22a.

  The resistance heating layer 22b is formed by first forming a thin conductive layer made of carbon particles or metal particles on the base layer 22a, and then laminating an insulating thin film made of a heat resistant resin such as polyimide resin on the conductive layer. It may be integrated.

  The carbon particles used for the resistance heating layer 22b may be ordinary carbon black powder, but may be carbon nanoparticles composed of at least one of carbon nanofibers, carbon nanotubes, and carbon microcoils.

  Further, the metal particles are particles made of Ag, Al, Ni, etc., and the shape thereof may be granular or may be a filament shape.

  The insulating layer 22d may be formed by applying an insulating material made of the same heat resistant resin as the base layer 22a such as polyimide resin.

  The electrode layer 22c may be formed by applying a conductive paste such as conductive ink or Ag, or may be formed by bonding a metal foil or a metal net.

Since the heat generating sheet 22s constituting the sheet heating element 22 is a thin sheet, its heat capacity is small and rapid heating is possible. The amount of heat generated can be arbitrarily set by the volume resistivity of the resistance heat generating layer 22b. . That is, the heat generation amount can be adjusted by the constituent material, shape, size, dispersion amount, etc. of the conductive particles constituting the resistance heat generation layer 22b. For example, the heat generation amount per unit area is 35 W / cm ² , It is possible to realize the planar heating element 22 that can output about 1200 W of electric power. In this case, the heat generating sheet 22s has a size of about 20 cm in width (axial direction) and 2 cm in length (circumferential direction), for example.

  Also, when a sheet heating element made of a metal filament such as stainless steel is used, the surface of the sheet heating element is uneven due to the presence of the filament, so when sliding with the inner peripheral surface of the fixing member 21, The surface is easily worn. However, since the heat generating sheet 22s has a flat surface with no irregularities as described above, it exhibits excellent durability against sliding with the inner peripheral surface of the fixing member 21. Furthermore, it is preferable to coat the surface of the resistance heating layer 22b of the heating sheet 22s with a fluororesin because durability against contact with the inner peripheral surface of the fixing member 21 is further improved.

  As an arrangement region of the heat generating sheet 22s on the inner peripheral surface of the fixing member 21, FIG. 1 shows a configuration in which the heat generating sheet 22s is disposed from the position opposite to the nip portion on the inner peripheral surface of the fixing member 21 to the front of the nip portion. However, the present invention is not limited to this. For example, the heat generating sheet 22s may be disposed up to the position of the nip portion, or may be disposed on the entire inner peripheral surface of the fixing member 21.

The fixing member 21 in the fixing device 20 is assembled in the following procedure, for example.
4 to 6 are diagrams illustrating the assembly of the fixing member. FIG. 5B is an enlarged view of FIG.
(Step S11)
First, as shown in FIG. 4, the heating sheet 22 s of the planar heating element 22 is attached with an adhesive along the outer peripheral surface of the heating element support member 23. At this time, as the adhesive, it is desirable to use an adhesive having a low thermal conductivity in order to prevent heat from flowing to the heating element support member 23.

  At this time, all of the plurality of electrode terminals 22e (electrode terminals 22e1, 22e2) connected to the electrode layer 22c are provided at one end of the heat generating sheet 22s corresponding to the circumferential direction of the fixing member 21. For example, on the side (end side) of one end portion (end portion opposite to the pressure member 31 (nip portion) side) corresponding to the circumferential direction of the fixing member 21 in the heat generating sheet 22s, the fixing member One electrode terminal 22e1, 22e2 is provided at each of both ends corresponding to the axial direction of 21.

  This is for the following reason. That is, the sheet heating element 22 is provided with at least two electrode terminals 22e for supplying power to the resistance heating layer 22b. For example, two electrode terminals 22e are provided at both ends of the heating sheet 22s. When provided one by one, it is necessary to connect a power harness or the like required for power supply to the electrode terminals 22e at both ends. At this time, the heat generating sheet 22s itself is a thin film, and since the rigidity of the heat generating sheet 22s itself is low, it is necessary to provide a terminal block for connecting a power supply harness at both ends of the heat generating sheet 22s, which increases the size of the apparatus. Therefore, in the embodiment, the apparatus is miniaturized by providing the electrode terminals 22e together at one end of the heat generating sheet 22s and supplying power.

  In addition, it is conceivable to arrange the electrode terminal 22e at the end of the heat generating sheet 22s corresponding to the axial direction of the fixing member 21, but when the heat generating sheet 22s is pasted along the outer peripheral surface of the heat generating member support member 23, The electrode terminal 22e also bends, and the electrode part for supplying power causes inconveniences such as deformation at the time of screw fastening, complication of the terminal member, and deterioration in assembling property.

  Therefore, in the embodiment, the plurality of electrode terminals 22e are arranged at one end portion of the heat generating sheet 22s corresponding to the circumferential direction of the fixing member 21, and thereby the heat generating sheet 22s is arranged along the outer peripheral surface of the heat generating member support member 23. Even when affixed, the electrode terminal 22e is not curved and good assemblability is realized.

(Step S12)
Next, as shown in FIG. 5, the heating sheet 22s in the vicinity of the electrode terminal 22e is bent so that the electrode terminal 22e faces the inner center of the fixing member 21, and then each of the electrode terminals 22e1 and 22e2 is connected to the terminal. The power supply line 25 is connected and fixed on the base stay 24. The connection and fixing of the electrode terminals 22e1 and 22e2 on the terminal block stay 24 may be performed by screw fastening as shown in FIG. Further, the planar heating element 22 is provided with a fixing terminal 22f extending for fixing the heating sheet 22s from the central portion of the end where the electrode terminal 22e of the heating sheet 22s is provided, and this fixing terminal 22f. Also, the terminal block stay 24 is fixed with screws.

  When the heating element support member 23 and the heating sheet 22s are not fixed with an adhesive or the like, the electrode terminal 22e and the fixing terminal 22f located on the opposite side of the heating sheet 22s from the nip portion are screwed to the terminal base stay 24. The fixing member 21 rotates so as to pull the heat generating sheet 22s toward the nip portion from the fixed side, whereby the heat generating sheet 22s is brought into contact with the heat generating body support member 23 and the inner peripheral surface of the fixing member 21. The fixing member 21 is stably brought into contact with the fixing member 21, and the fixing member 21 can be efficiently heated.

(Step S13)
Next, as shown in FIG. 6, the core holding member 28 is mounted so that the terminal block stay 24 is accommodated in one of the H-shaped recessed portions, and is further in contact with the other recessed portion of the H-shaped. The member 26 is mounted to form an internal mechanism portion on the fixing member 21 side.
Finally, the internal mechanism portion is inserted into the inner peripheral side of the fixing member 21 and arranged as shown in FIG. 1 to complete the assembly of the fixing device 20 on the fixing member 21 side.

The fixing device 20 configured as described above has the following operational effects.
As shown in FIG. 1, the fixing device 20 includes first temperature detection means 41, second temperature detection means 42, and tension fluctuation means 55. Further, the tension changing means 55 is configured as shown in FIG. 7 and includes a pressing member 50 and a cam 51 having an elliptical planar shape. The pressing member 50 is a member attached to the inner peripheral side of the fixing member 21 and having an R shape along the shape of the inner peripheral surface of the fixing member 21. The pressing member 50 is urged toward the cam 51 by urging means (not shown). By rotating the cam 51, the pressing force of the pressing member 50 to the fixing member 21 varies.
The fixing device 20 uses the temperature of the pressing member 50 based on the temperature detected by the first temperature detecting means 41 and the temperature difference between the temperature detected by the first temperature detecting means 41 and the temperature detected by the second temperature detecting means 42. The pressing force against the fixing member 21 can be adjusted. However, the pressing member 50 and the cam 51 as the tension varying means 55 are only examples, and are not limited to those illustrated in FIG. 7, and any mechanism that can vary the tension of the fixing member 21 from the inner peripheral side of the fixing member 21. Good.

  First, when the image forming apparatus receives an output signal (for example, when there is a print request to the image forming apparatus by operation of a user's operation panel or communication from a personal computer), in the fixing device 20, the pressure member 31 is fixed to the fixing member 21. Is pressed by the contact member 26 to form a nip portion.

  Next, when the pressing member 31 is driven to rotate in the clockwise direction in FIG. 1 by a driving device (not shown), the fixing member 21 is also rotated and rotated in the clockwise direction. At this time, the planar heating element 22 is in a state of being in contact with and sliding on the inner peripheral surface of the fixing member 21 while being supported by the heating element support member 23.

  In synchronism with this, power is supplied to the sheet heating element 22 from the external power supply or the internal power storage device through the feeder line 25, the heating sheet 22s generates heat, and the fixing member 21 is in contact with the heating sheet 22s. Heat is transferred efficiently and heated rapidly. Note that the operation of the driving device and the heating by the planar heating element 22 do not need to be started at the same time, but may be started with an appropriate time difference.

  At this time, it is detected by the second temperature detecting means arranged in contact or non-contact from the heating element support member 23 on the upstream side of the nip portion 21n and outside the fixing member 21 or inside the heating sheet 22s. The heating by the planar heating element 22 is controlled so that the nip portion 21n is at a predetermined temperature depending on the temperature of the recording medium. Paper is started.

  In this temperature raising process, it is preferable that the temperature of the sheet heating element 22 and the temperature of the fixing member 21 are the same. However, an insulating layer exists between the sheet heating element 22 and the fixing member 21. Therefore, in practice, a temperature difference occurs in each temperature rising process. In addition, if there is a minute gap between the sheet heating element 22 and the fixing member 21, the heat conduction deteriorates, and abnormal heating of the sheet heating element 22 occurs. In the embodiment, by increasing the tension of the fixing member 21, the planar heating element 22 and the fixing member 21 are brought into close contact with each other so that the gap is not generated.

  In particular, when the temperature of the resistance heating portion 22 b of the planar heating element 22 is quickly raised during the temperature raising process, a temperature difference is generated between the planar heating element 22 and the fixing member 21. For example, in the state where the fixing member 21 is colder, the planar heating element 22 is lit at a higher lighting rate, so this temperature difference is likely to increase. Even when the contact between the sheet heating element 22 and the fixing member 21 is weak, the temperature difference between the sheet heating element 22 and the fixing member 21 becomes large.

  When the temperature difference between the sheet heating element 22 and the fixing member 21 becomes large and the contact between the sheet heating element 22 and the fixing member 21 is weak, the heat from the sheet heating element 22 to the fixing member 21 is reduced. Conduction is inferior, and the temperature of the insulating layer (base layer 22a or insulating layer 22d) of the planar heating element 22 increases. If the temperature of the insulating layer rises too much, the insulating layer may be heated to a temperature higher than the heat resistant temperature, and the insulating layer may be deformed or peeled off. As a result, the function may not be maintained, for example, an electrical short circuit may occur in the sheet heating element 22 during operation of the fixing device 20.

In the embodiment, the temperature T ₁ (surface temperature of the planar heating element 22) detected by the first temperature detection unit 41 and the temperature T ₂ (outer surface temperature of the fixing member 21) detected by the second temperature detection unit 42 are used. ) And the temperature T ₁ detected by the first temperature detection means 41 reaches a certain temperature T ₀ , the surface temperature of the sheet heating element 22 (the temperature T ₁ detected by the first temperature detection means 41). ) And the temperature of the fixing member 21 (temperature T ₂ detected by the second temperature detecting means 42), the tension varying means 55 adjusts the tension of the fixing member 21. Here, the temperature T ₀ is a target temperature. In other words, the pressing force between the sheet heating element 22 and the fixing member 21 is controlled by adjusting the tension of the fixing member 21 with the tension changing means 55.

For example, when the insulating layer is polyimide, the upper limit temperature (heat resistant temperature) is 250 ° C., so T _{0 is set} to 200 ° C. When the temperature T ₁ reaches T ₀ (200 ° C.), an upper limit is set for the lighting rate of the planar heating element 22. Then, when the temperature difference ΔT exceeds the predetermined temperature difference ΔT ₁₂ , the pressing force P is controlled to be higher than the predetermined pressing force P _1, and the heat from the planar heating element 22 to the fixing member 21 is controlled. Promotes conduction. Here, the temperature difference ΔT ₁₂ is a target temperature difference. Further, the temperature difference [Delta] T is controlled against force pushing the pushing force P ₁ below in the case of a predetermined temperature difference [Delta] T ₁₂ less. Such adjustment is controlled by the control unit 45.

For example, when the temperature difference ΔT exceeds a predetermined temperature difference ΔT ₁₂ , the tension applied to the fixing member 21 is determined by rotating the cam 51 that contacts the pressing member 50, thereby pressing the cam 51. A pressing force is applied to the fixing member 21 through the contact member 50. For example, the maximum value P _max of the pressing force is obtained when the tip 51t of the cam 51 is pushed against the pressing member 50 (see FIG. 7A).

On the other hand, if the temperature difference [Delta] T is a predetermined temperature difference [Delta] T ₁₂ or less, and the distal end portion 51t of the cam 51 Impale portion opposite to the contact member 50 pressed. In this case, the minimum value P _min of the pressing force is obtained when the portion of the cam 51 opposite to the tip 51t is vertically projected to the pressing member 50 (see FIG. 7B). The pressing force P ₁ may be appropriately determined between P _max and P _min .

The above control is represented by a flow as shown in FIG.
FIG. 8 is a flowchart for explaining the control of the pressing force.
The controller 45 detects that the temperature detected by the first temperature detector 41 is higher than the target temperature T _0, and the temperature difference between the temperature detected by the first temperature detector 41 and the temperature detected by the second temperature detector 42 is When the temperature difference is higher than the target temperature difference ΔT ₁₂ , a pressure larger than the predetermined pressure value P _{1 is} applied to the fixing member 21 by the pressing member 50.

First, the control unit 45 detects the temperature T ₁ (surface temperature of the planar heating element 22) detected by the first temperature detection means 41 (S100). Further, to detect the _{T 2} by the second temperature detecting means 42. Thereby, ΔT (ΔT = T ₁ −T ₂ ) is determined. Here, if the temperature T ₁ is higher than the temperature T ₀ , the process proceeds to the next step, and the temperature difference ΔT and ΔT ₁₂ are compared (S101). Temperature _{T 1} is in the case of temperature _{T 0} or less, the pressing force P to _{P 1} below (S200).

Then, the temperature difference [Delta] T may [Delta] T ₁₂ larger than the pressing force P is greater than _{P 1} (S102). The temperature difference [Delta] T is the case of [Delta] T ₁₂ below, the pressing force P to _{P 1} or less (S201).

  Thus, the control unit 45 determines the temperature detected by the first temperature detection means 41 and the temperature difference ΔT between the temperature detected by the first temperature detection means 41 and the temperature detected by the second temperature detection means 42. Thus, the pressing force against the fixing member 21 is adjusted by rotating the cam 51.

Thereby, even if the temperature of the planar heating element 22 exceeds T ₀ , the contact pressure between the planar heating element 22 and the fixing member 21 is adjusted, and the surface temperature of the planar heating element 22 and the fixing member 21 are adjusted. The temperature difference ΔT with respect to the temperature is controlled to be constant (feedback control). As a result, a predetermined amount of heat is conducted from the planar heating element 22 to the fixing member 21 so that the temperature of the planar heating element 22 does not reach the upper limit temperature of the insulating layer of the planar heating element 22. . Thereby, deformation and peeling of the insulating layer of the planar heating element 22 are less likely to occur, and the planar heating element 22 operates stably.

In FIG. 8, ΔT is used as the control parameter. However, the control method is not limited to this, and control may be performed based on the ratio of T ₁ and T _2. The pressing force P corresponding to each section may be set.

  In the fixing device 20, since the heat capacities of the fixing member 21 and the sheet heating element 22 are small, the warm-up time and the first print time can be shortened while saving energy. Further, since the heat generating sheet 22s in the sheet heating element 22 is a resin-based sheet, the stress caused by the rotation and vibration of the pressure member 31 repeatedly acts on the heat generating sheet 22s, and the heat generating sheet 22s is repeatedly bent. Even if it breaks, it will not be damaged by fatigue and can be operated for a long time.

  When there is no output signal to the image forming apparatus, the pressure member 31 and the fixing member 21 are normally non-rotated and the sheet heating element 22 is not energized in order to reduce power consumption. When re-output is desired to be started (returned), the sheet heating element 22 can be energized even when the pressure member 31 and the fixing member 21 are not rotated. In this case, the sheet heating element 22 is energized to keep the entire fixing member 21 warm.

Next, a detailed configuration of the heat generating sheet 22s in the planar heating element 22 used in the embodiment will be described.
That is, the heat generating sheet 22s may have the resistance heat generating layer 22b formed on the entire main surface of the base layer 22a or a certain region, but in each of a plurality of regions arbitrarily divided on the main surface of the base layer 22a. The resistance heating layer 22b is preferably formed so as to be able to generate heat independently. 9 to 11 show examples of the configuration.

FIG. 9A is a schematic top view showing a configuration example (1) of the planar heating element.
Here, a state in which the planar heating element 22 is unfolded on a flat surface and viewed from above is shown before being attached to the heating element support member 23. In the drawing, the horizontal direction is the width direction corresponding to the axial direction of the fixing member 21, and the vertical direction is the length direction corresponding to the circumferential direction of the fixing member 21.

  In FIG. 9A, the heat generating sheet 22s is roughly divided into three in the width direction (axial direction) on the main surface, and six divided regions are further divided into two in the length direction (circumferential direction). ing. Here, when the six divided regions are viewed as a matrix matrix in which the length direction (circumferential direction) includes row components and the width direction (axial direction) includes column components (FIG. 9B), (1, 2) A resistance heating layer 22b1 having a predetermined width and length is formed in the component divided region (region corresponding to the central portion in the axial direction of the fixing member 21), and the (2, 1) component and (2, 3) component divided regions are formed. A resistance heating layer 22b2 having a predetermined width and length is formed in each of the regions corresponding to both axial ends of the fixing member 21.

  In addition, in the divided regions of the (1, 1) component and the (1, 3) component, an electrode layer 22c connected to the resistance heating layer 22b1 is formed, and each electrode layer 22c has a heating sheet 22s. An electrode terminal 22e1 extending from one side (lower side in the figure) is provided to form a first heat generating circuit.

  In addition, an electrode layer 22c that connects the two resistance heating layers 22b2 is formed in the divided region of the (2, 2) component, and further, the length direction of the heating sheet 22s ( The electrode layer 22c extending in the circumferential direction and extending toward the one side (the lower side in the figure) is connected, and each electrode layer 22c has an electrode terminal 22e2 extending from the one side of the heat generating sheet 22s. A second heat generation circuit is formed.

  Further, an insulating layer 22d is provided between the first heat generating circuit and the second heat generating circuit to prevent short-circuit between them.

  In the sheet heating element 22 having the configuration shown in FIG. 9A, when energized from the electrode terminal 22e1, heat is generated as Joule heat due to the internal resistance of the resistance heating layer 22b1, and the electrode layer 22c does not generate heat due to low resistance. Only the divided regions of the (1, 2) component of the heat generating sheet 22s generate heat, and the central portion in the axial direction of the fixing member 21 can be heated.

  Further, when energized from the electrode terminal 22e2, heat is generated as Joule heat due to the internal resistance of the resistance heating layer 22b2, and the electrode layer 22c does not generate heat due to low resistance. Therefore, the (2, 1) component and (2 3) Only the divided region of the component generates heat, and both end portions in the axial direction of the fixing member 21 can be heated.

  Therefore, when a small-size (narrow width) recording medium P is passed through the fixing device 20, only the electrode terminal 22e1 is energized to heat only the central portion in the axial direction of the fixing member 21 and to widen the width. When the recording medium P is passed, the electrode terminals 22e1 and 22e2 are energized to heat the entire axial width of the fixing member 21, thereby reducing the energy consumption and appropriately depending on the width of the recording medium P. Fixing is possible. Further, since the amount of heat generated by the sheet heating element 22 can be controlled in accordance with the size of the recording medium P, the temperature of the non-sheet passing portion does not rise excessively even if small size paper is continuously fed. It is possible to prevent the device from being stopped for protection and the productivity from being lowered. Further, by providing the positional relationship of the different heat generating portions with the integrated planar heat generating element 22, a heat generating element having a smaller temperature deviation in the axial direction than that formed by a separate heat generating element can be obtained.

  In addition, in the heat generating sheet 22s, at the end portions of the resistance heat generating layers 22b1 and 22b2, heat flows out to the insulating layer 22d and the electrode layer 22c having a relatively high thermal conductivity, so that the amount of heat generation tends to be low. It is in. Therefore, as shown in FIG. 9A, in the width direction (axial direction) of the heat generating sheet 22s, the boundary between the resistance heating layer 22b1 at the center and the resistance heating layer 22b2 at the end is the same surface. When the currents 22e1 and 22e2 were energized, the temperature distribution in the axial direction of the fixing member 21 caused a temperature drop at the boundary between the resistance heating layer 22b1 and the resistance heating layer 22b2, and an abnormal image such as a fixing failure occurred. Therefore, it is preferable to adopt the configuration of FIG. 10 or FIG. 11 to improve this problem.

FIG. 10 is a schematic top view showing a configuration example (2) of the planar heating element.
The basic configuration of the planar heating element 22 shown in FIG. 10 is the same as that shown in FIG. 9A, but a part of the resistance heating layer 22b1 and the resistance heating layer 22b2 is the width direction of the heating sheet 22s. The difference is that they overlap in the (axial direction) to form an overlap region. Thereby, it is possible to prevent a temperature drop at the boundary between the resistance heating layer 22b1 and the resistance heating layer 22b2 when the electrode terminals 22e1 and 22e2 are energized.

FIG. 11 is a schematic top view illustrating a configuration example (3) of the planar heating element.
The basic configuration of the planar heating element 22 shown in FIG. 11 is the same as that shown in FIG. 10, but in the overlapping region of the resistance heating layer 22b1 and the resistance heating layer 22b2, each of the resistance heating layers 22b1 and 22b2 and electrodes The difference is that the amount of overlapping of the resistance heating layers 22b1 and 22b2 is adjusted by inclining the boundary line with the layer 22c in different directions with respect to the length direction (circumferential direction).

  In the configuration of FIG. 10, the area ratio of the overlapping regions of the resistance heating layers 22b1 and 22b2 is constant in the width direction (axial direction), and the variation in the amount of heat generation increases with the variation in the overlapping width. However, in the configuration of FIG. 11, the area ratio in the overlapping region of the resistance heating layers 22b1 and 22b2 is changed at a constant rate in the width direction (axial direction) to reduce the influence of adjustment of heat generation distribution and component variations. Thus, the temperature uniformity in the entire axial direction is improved, and the problems caused by the configuration of FIG. 10 are improved.

  In the heat generating sheet 22s having the configuration shown in FIGS. 9 to 11, first, only the regions corresponding to the resistance heating layers 22b1 and 22b2 on the main surface of the base layer 22a are exposed to form the resistance heating layers 22b1 and 22b2 by coating. Next, an insulating layer 22d made of only a heat-resistant resin is formed by application in a state where only the region corresponding to the insulating layer 22d is exposed, then only the region corresponding to the electrode layer 22c is exposed, and a conductive paste is applied to expose the electrode layer 22c. This is possible by forming Therefore, the resistance heating layers 22b1 and 22b2 having an arbitrary shape can be formed by adjusting the exposed shape of the regions corresponding to the resistance heating layers 22b1 and 22b2.

  Further, the sheet heating element 22 used in the embodiment is formed by laminating a plurality of heating sheets 22s, and the heating sheets 22s are formed in any region on the main surface of each base layer 22a in the resistance heating layer 22b. Are preferably formed so that they can generate heat independently. FIG. 12 shows a specific configuration thereof.

FIG. 12 is an exploded perspective view showing a configuration example (4) of the planar heating element.
In FIG. 12, a planar heating element 22 is formed by laminating a first heating sheet 22s, an insulating sheet made of an insulating layer 22d, and a second heating sheet 22s in order from the top in the figure.

  Here, the main surface of the first heat generating sheet 22s is divided into three in the width direction (axial direction), the resistance heat generating layer 22b1 is formed in the central divided region, and the resistance is formed in each of the divided regions on both sides thereof. An electrode layer 22c connected to the heat generating layer 22b1 is formed. The main surface of the second heat generating sheet 22s is divided into five in the width direction (axial direction), and the resistance heat generating layer 22b2 is formed in the second and fourth divided regions in the width direction (axial direction). An electrode layer 22c connected to the resistance heating layer 22b2 is formed in each of the remaining divided regions.

  The first heat generating sheet 22s and the second heat generating sheet 22s are stacked with an insulating sheet made of an insulating layer 22d interposed therebetween, and an independent first heat generating circuit is formed on the first heat generating sheet 22s. An independent second heat generating circuit is formed on the second heat generating sheet 22s.

  As a result, when the first heat generating circuit is energized, heat is generated as Joule heat by the internal resistance of the resistance heat generating layer 22b1, and only the central region in the width direction (axial direction) of the first heat generating sheet 22s generates heat. The central portion of the member 21 in the axial direction can be heated. When the second heat generating circuit is energized, heat is generated as Joule heat by the internal resistance of the resistance heat generating layer 22b2, and only the both end regions in the width direction (axial direction) of the second heat generating sheet 22s generate heat. Both axial ends of the member 21 can be heated.

  Like the planar heating element 22 shown in FIG. 9 to FIG. 11, the area of the entire planar heating element 22 is increased in order to secure a necessary amount of heat when it is divided up to the length direction (circumferential direction), In some cases, the fixing member 21 having a small diameter cannot be used. Therefore, as shown in FIG. 12, different heat generation distributions are obtained in the same manner as the planar heating element 22 shown in FIGS. 9 to 11 by stacking the heating sheets 22 s of different heating parts in the thickness direction of the planar heating element 22. It is possible to achieve a high output while saving space (reducing the size) while realizing the planar heating element 22 that can be obtained.

  By the way, in the fixing device 20, during rotation, the fixing member 21 is pulled by the pressure member 31 at the nip portion, so that the fixing member 21 on the upstream side of the nip portion becomes a tension side to which tension is applied, and the inner peripheral surface of the fixing member 21 is The sheet heating member 22 slides on the sheet heating element 22 while being in pressure contact with the heating element support member 23. On the other hand, the tension is not applied to the fixing member 21 on the downstream side of the nip portion, and the fixing member 21 is in a relaxed state. If an attempt is made to increase the speed of the apparatus in this state, the fixing member 21 on the downstream side of the nip portion. As a result, the degree of slackening of the fixing member 21 becomes serious, and the rotational running stability of the fixing member 21 is hindered.

  Therefore, it is preferable that the fixing device 20 includes a rotation support member that supports the rotation state of the fixing member 21 on the inner peripheral side of the fixing member 21 and at least on the downstream side of the nip portion.

FIG. 13 is a schematic cross-sectional view illustrating an arrangement example of the rotation support member, the planar heating element, and the contact member in the fixing device. Here, the example of arrangement | positioning of the rotation support member, the planar heating element 22, and the contact member 26 is shown.
FIG. 13A is a configuration example in which a planar heating element 22 is provided on the inner periphery of a metal body, for example, a stainless thin film pipe, as the rotation support member 27A, and the fixing member 21 is supported on the outer periphery side of the rotation support member 27A. . With this configuration, not only the rotation running stability of the fixing member 21 can be ensured, but also the fixing member 21 can be supported by the highly rigid metal rotation support member 27A, so that assembly handling is easy. Further, since the sheet heating element 22 does not slide in direct contact with the fixing member 21, the protective layer (sliding layer) or insulating layer on the surface of the sheet heating element 22 slides and wears, and the resistance heating layer 22b. And the risk of electrical leakage due to exposure of conductors such as the electrode layer 22c is eliminated. In addition, since a metal body is provided as the rotation support member 27A, there is a disadvantage that the heat capacity is increased and the temperature increase rate during warm-up is slower than that of the configuration of FIG.

  13B, the function of the rotation support member 27A itself is the same as that of FIG. 13A, but heat conduction to the fixing member 21 is provided by providing a planar heating element 22 on the outer peripheral side of the rotation support member 27A. Is a configuration improved from that of FIG. However, heat outflow (loss) from the back surface of the planar heating element 22 (rotation support member 27A side) is unavoidable.

  FIG. 13C shows a configuration in which a rotation support member 27B made of a solid resin having a lower thermal conductivity than the metal body is used instead of the rotation support member 27A in FIG. 13B. Thereby, it is possible to suppress the heat outflow (loss) from the back surface (rotation support member 27B side) of the planar heating element 22, but generally the heat resistance of the resin is lower than that of the metal, and the heat resistance is high. Resin is expensive and disadvantageous in cost.

  FIG. 13D shows a configuration in which a rotation support member 27C made of a polyimide resin foam is used instead of the solid resin rotation support member 27B in FIG. 13C. By using a polyimide resin foam, it is possible to ensure the heat insulation and rigidity necessary for the rotation support member.

  Further, as shown in FIG. 13 (e), it is preferable to provide a resin member 27D supplementarily on the inner peripheral portion of the rotation support member 27C made of a polyimide foam because rigidity is further improved.

14 to 16 are schematic cross-sectional views illustrating the configuration of the fixing device according to the second embodiment. Here, the configuration of FIG. 13A is added to the fixing device of FIG.
That is, the fixing device 20 has the same basic configuration as that shown in FIG. 1, but includes a pipe-shaped rotation support member 27A provided on the inner peripheral side of the fixing member 21 and an inner peripheral side of the rotation support member 27A. Therefore, the heat insulating support member 29 is provided on the H-shaped outer surface of the core support member 28 so as to be arranged on the downstream side of the nip portion. In addition, the heat insulation instruction | indication member 29 is not provided in the position in which the tension | tensile_strength fluctuation | variation means 55 is provided, and the opening part 52 should just be provided in 27 A of rotation support members.

  Here, the rotation support member 27 </ b> A has a pipe shape made of a thin metal such as iron or stainless steel having a thickness of 0.1 to 1 mm, for example, and the outer diameter thereof is 0.5 mm larger than the inner diameter of the fixing member 21. It is about 1 mm smaller. Further, the nip portion side is cut and opened in the axial direction on the outer peripheral surface of the rotation support member 27A, and the end portion is folded to the core support member 28 side so as not to contact the nip portion.

  The heat insulating support member 29 has heat resistance sufficient to withstand the heat of the fixing member 21 via the rotation support member 27A on the exit side of the nip portion, and heat outflow (loss) from the rotation support member 27A in contact with the fixing member 21. It has heat insulation to prevent, and strength sufficient to support the rotation support member 27A so as not to be deformed when the rotating fixing member 21 contacts the rotation support member 27A. It is preferable that it is the same polyimide resin as 23.

  In addition, as shown in FIG. 15, the rotation support member 27A is provided with an opening 27a by removing the outer peripheral surface of a certain region upstream of the nip portion. Accordingly, as shown in FIG. 16, when the internal mechanism portion of the fixing member 21 is configured, the entire surface of the sheet heating element 22 is exposed from the opening 27a, and the sheet heating element 22 becomes the fixing member. 21 is arranged close to the inner peripheral surface of 21. An opening 52 is provided on the side opposite to the opening 27a so that the pressing member 50 can protrude.

  Accordingly, the sheet heating element 22 (heating sheet 22s) is supported by the heating element support member 23 and is disposed close to the inner peripheral surface of the fixing member 21 with a predetermined gap δ. Since the gap δ is equal to or less than the thickness of the rotation support member 27A, that is, 0 <δ ≦ 1 mm, the problem in FIG. 13A can be improved and the fixing member 21 can be efficiently heated. .

  The fixing device 20 of the second embodiment shown in FIG. 14 shortens the warm-up time and the first print time while saving energy in addition to the operational effects of the fixing device 20 (FIG. 1) of the first embodiment. Can do. Further, since the heat generating sheet 22s in the sheet heating element 22 is a resin-based sheet, the stress caused by the rotation and vibration of the pressure member 31 repeatedly acts on the heat generating sheet 22s, and the heat generating sheet 22s is repeatedly bent. Even if it breaks, it will not be damaged by fatigue and can be operated for a long time. Further, in the sheet heating element 22, it is possible to perform efficient temperature control corresponding to the size of the recording medium P through which the paper is passed by generating heat at different heating portions in the axial direction of the fixing member 21. In addition to this, by providing the rotation support member 27A (the heat insulation support member 29 as required), the rotational running stability of the fixing member 21 can be improved, and the speed can be increased. Further, since the temperature in the axial direction of the fixing member 21 can be supplementarily performed by heat conduction in the axial direction of the fixing member 21 in the rotation support member 27A, it is possible to cope with a higher speed apparatus. Become.

Next, the image forming apparatus according to the present invention will be described.
FIG. 17 is an overall configuration diagram showing the configuration of the image forming apparatus.
As shown in FIG. 17, the image forming apparatus 1 is a tandem type color printer. Four bottles 102Y, 102M, 102C, and 102K corresponding to the respective colors (yellow, magenta, cyan, and black) are detachably (replaceable) installed in the bottle housing portion 101 above the image forming apparatus main body 1. ing.

  An intermediate transfer unit 85 is disposed below the bottle housing portion 101. Image forming units 4Y, 4M, 4C, and 4K corresponding to the respective colors (yellow, magenta, cyan, and black) are arranged in parallel so as to face the intermediate transfer belt 78 of the intermediate transfer unit 85.

  Photosensitive drums 5Y, 5M, 5C, and 5K are disposed in the image forming units 4Y, 4M, 4C, and 4K, respectively. Further, around each of the photosensitive drums 5Y, 5M, 5C, and 5K, a charging unit 75, a developing unit 76, a cleaning unit 77, a charge eliminating unit (not shown), and the like are disposed. Then, an image forming process (charging process, exposure process, development process, transfer process, cleaning process) is performed on each of the photoconductive drums 5Y, 5M, 5C, and 5K. An image of each color is formed on 5K.

  The photosensitive drums 5Y, 5M, 5C, and 5K are rotationally driven in a clockwise direction in FIG. 17 by a drive motor (not shown). Then, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K are uniformly charged at the position of the charging unit 75 (a charging process).

  Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach the irradiation position of the laser light L emitted from the exposure unit 3, and electrostatic latent images corresponding to the respective colors are formed by exposure scanning at this position. (It is an exposure process.)

  Thereafter, the surfaces of the photosensitive drums 5Y, 5M, 5C, and 5K reach a position facing the developing device 76, and the electrostatic latent image is developed at this position to form toner images of each color (developing process). .)

  Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach the positions facing the intermediate transfer belt 78 and the first transfer bias rollers 79Y, 79M, 79C, and 79K, and at these positions, the photoconductive drums 5Y, 5M. The toner images on 5C and 5K are transferred onto the intermediate transfer belt 78 (this is a primary transfer process). At this time, a small amount of untransferred toner remains on the photosensitive drums 5Y, 5M, 5C, and 5K.

  Thereafter, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing the cleaning unit 77, and untransferred toner remaining on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. 77 is mechanically collected by a cleaning blade (cleaning process).

Finally, the surfaces of the photoconductive drums 5Y, 5M, 5C, and 5K reach a position facing a neutralization unit (not shown), and the residual potential on the photoconductive drums 5Y, 5M, 5C, and 5K is removed at this position. The
Thus, a series of image forming processes performed on the photosensitive drums 5Y, 5M, 5C, and 5K is completed.

Thereafter, the toner images of the respective colors formed on the respective photosensitive drums through the developing process are transferred onto the intermediate transfer belt 78 in an overlapping manner. In this way, a color image is formed on the intermediate transfer belt 78.
Here, the intermediate transfer unit 85 includes an intermediate transfer belt 78, four primary transfer bias rollers 79Y, 79M, 79C, and 79K, a secondary transfer backup roller 82, a cleaning backup roller 83, a tension roller 84, and an intermediate transfer cleaning unit 80. , Etc. The intermediate transfer belt 78 is stretched and supported by three rollers 82 to 84 and is endlessly moved in the direction of the arrow in FIG.

The four primary transfer bias rollers 79Y, 79M, 79C, and 79K sandwich the intermediate transfer belt 78 with the photosensitive drums 5Y, 5M, 5C, and 5K, respectively, thereby forming primary transfer nips. Then, a transfer bias reverse to the polarity of the toner is applied to the primary transfer bias rollers 79Y, 79M, 79C, and 79K.
The intermediate transfer belt 78 travels in the direction of the arrow and sequentially passes through the primary transfer nips of the primary transfer bias rollers 79Y, 79M, 79C, and 79K. In this way, the toner images of the respective colors on the photosensitive drums 5Y, 5M, 5C, and 5K are primarily transferred while being superimposed on the intermediate transfer belt 78.

Thereafter, the intermediate transfer belt 78 onto which the toner images of the respective colors are transferred in an overlapping manner reaches a position facing the secondary transfer roller 89. At this position, the secondary transfer backup roller 82 sandwiches the intermediate transfer belt 78 between the secondary transfer roller 89 and forms a secondary transfer nip. The four color toner images formed on the intermediate transfer belt 78 are transferred onto the recording medium P conveyed to the position of the secondary transfer nip. At this time, untransferred toner that has not been transferred to the recording medium P remains on the intermediate transfer belt 78.
Thereafter, the intermediate transfer belt 78 reaches the position of the intermediate transfer cleaning unit 80. At this position, the untransferred toner on the intermediate transfer belt 78 is collected.
Thus, a series of transfer processes performed on the intermediate transfer belt 78 is completed.

Here, the recording medium P transported to the position of the secondary transfer nip is transported from the paper feeding unit 12 disposed below the apparatus main body 1 via the paper feeding roller 97 and the registration roller pair 98. It is a thing.
Specifically, a plurality of recording media P such as transfer paper are stored in the paper supply unit 12 in an overlapping manner. When the paper feed roller 97 is driven to rotate counterclockwise in FIG. 17, the uppermost recording medium P is fed between the rollers of the registration roller pair 98.

  The recording medium P conveyed to the registration roller pair 98 is temporarily stopped at the position of the roller nip of the registration roller pair 98 that has stopped rotating. Then, the registration roller pair 98 is rotationally driven in synchronization with the color image on the intermediate transfer belt 78, and the recording medium P is conveyed toward the secondary transfer nip. In this way, a desired color image is transferred onto the recording medium P.

Thereafter, the recording medium P on which the color image is transferred at the position of the secondary transfer nip is conveyed to the position of the fixing device 20. At this position, the color image transferred to the surface is fixed on the recording medium P by heat and pressure generated by the fixing member 21 and the pressure member 31.
Thereafter, the recording medium P is discharged out of the apparatus through a pair of paper discharge rollers 99. The transferred P discharged from the apparatus by the discharge roller pair 99 is sequentially stacked on the stack unit 100 as an output image.
Thus, a series of image forming processes in the image forming apparatus is completed.

  As described above, since the image forming apparatus of the present invention includes the fixing device 20 described above, the warm-up time and the first print time are short, and even when the size of the recording medium P changes, the energy consumption is appropriately suppressed. Image formation is possible, and even when the speed of the apparatus is increased, it is possible to prevent problems such as fixing failure from occurring.

  As described above, according to the present invention, since the insulating layer is provided between the heating portion of the planar heating element and the fixing member, the first temperature can be obtained even when a temperature difference occurs between the planar heating element and the fixing member. The pressing force of the pressing member is adjusted based on the temperature difference between the temperature of the planar heating element detected by the detecting means and the temperature detected by the first temperature detecting means and the temperature detected by the second temperature detecting means. As a result, a fixing device capable of fixing without generating a minute gap area between the planar heating element and the fixing member without exceeding the heat resistance temperature of the planar heating element and an image forming apparatus including the fixing device are realized. .

  Although the present invention has been described with the embodiments shown in the drawings, the present invention is not limited to the embodiments shown in the drawings, and other embodiments, additions, modifications, deletions, etc. Can be changed within the range that can be conceived, and any embodiment is included in the scope of the present invention as long as the effects and advantages of the present invention are exhibited.

  Although the embodiments have been described above, the present invention is not limited to the embodiments shown in the drawings. Other embodiments, additions, changes, deletions, and the like can be changed within a range that can be conceived by those skilled in the art. Any aspect is included in the scope of the present invention as long as the operations and effects of the present invention are exhibited.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Exposure part 4Y, 4M, 4C, 4K Image forming part 5Y, 5M, 5C, 5K Photosensitive drum 12 Paper feed part 20 Fixing device 21 Fixing member (fixing sleeve)
21n Nip 22 Sheet heating element 22a Base layer 22b, 22b1, 22b2 Resistance heating layer 22c Electrode layer 22d Insulating layer 22e, 22e1, 22e2 Electrode terminal 22f Fixed terminal 22s Heating sheet 23 Heating element support member 24 Terminal block stay 25 Feed line 26 Contact member 27A, 27B, 27C Rotating body support member 27a Opening portion 27D Resin member 28 Core holding member 29 Heat insulation support member 31 Pressure member (pressure roller)
41 First temperature detecting means 42 Second temperature detecting means 50 Pushing member 51 Cam 52 Opening part 55 Tension varying means 75 Charging part 76 Developing part 77 Cleaning part 78 Intermediate transfer belt 79Y, 79M, 79C, 79K First transfer bias roller 80 Intermediate transfer cleaning unit 82 Secondary transfer backup roller 83 Cleaning backup roller 84 Tension roller 85 Intermediate transfer unit 97 Paper feed roller 98 Registration roller pair 99 Paper discharge roller pair 100 Stack unit 101 Bottle storage unit 102Y, 102M, 102C, 102K Toner Bottle L Laser light P Recording medium T Toner

Japanese Patent Laid-Open No. 11-2982 JP-A-4-44075 JP-A-8-262903 JP-A-10-213984 JP 2007-334205 A JP 2008-154822 A JP 2008-216928 A JP 2011-133839 A

Claims (10)

A fixing member for a rotating endless belt;
A pressure member in contact with the outer peripheral surface of the fixing member;
An abutting member disposed on an inner peripheral side of the fixing member and abutting the pressure member via the fixing member to form a nip portion;
A sheet heating element that is disposed in contact with or close to the fixing member on the inner peripheral side of the fixing member, and directly or indirectly heats the fixing member;
A heating element support member disposed on an inner peripheral side of the fixing member so as to sandwich the planar heating element between the fixing member and supporting the planar heating element at a predetermined position;
A first temperature detecting means disposed between the planar heating element and the heating element support member for detecting a surface temperature of the planar heating element;
A second temperature detecting means disposed at a position facing the first temperature detecting means across the fixing member and detecting an outer peripheral surface temperature of the fixing member;
Tension varying means for varying the tension of the fixing member by applying a pressing force to the fixing member from the inner peripheral side of the fixing member;
A controller that operates the tension varying means based on the temperature detected by the first temperature detecting means and the temperature detected by the second temperature detecting means to adjust the tension of the fixing member;
A fixing device comprising:   The controller is configured such that the temperature detected by the first temperature detecting means is higher than the target temperature, and the temperature difference between the temperature detected by the first temperature detecting means and the temperature detected by the second temperature detecting means is a target temperature. The fixing device according to claim 1, wherein when the difference is higher than the difference, the tension changing unit is operated to apply a pressing force larger than a predetermined pressure value to the fixing member.   The tension varying means has a pressing member disposed on the inner peripheral side of the fixing member, and a cam that contacts the pressing member, and the cam rotates so that the pressing member The fixing device according to claim 1, wherein the pressing force against the fixing member varies.   In the planar heating element, a resistance heating layer in which conductive particles are dispersed in a heat-resistant resin and an electrode layer that supplies power to the resistance heating layer are formed on an insulating base layer. The fixing device according to claim 1, further comprising a heat generating sheet having a predetermined width and length corresponding to an axial direction and a circumferential direction of the fixing member and exhibiting flexibility. .   5. The fixing according to claim 4, wherein the heat generating sheet is formed so that the resistance heat generating layer can independently generate heat in each of a plurality of regions arbitrarily divided on the main surface of the base layer. apparatus.   The planar heating element is formed by laminating a plurality of heating sheets, and the plurality of heating sheets are formed in any region on the main surface of each base layer so that the resistance heating layer can independently generate heat. The fixing device according to claim 4, wherein the fixing device is formed.   5. The planar heating element has all of a plurality of electrode terminals connected to the electrode layer at one end of the heating sheet corresponding to the circumferential direction of the fixing member. The fixing device according to claim 6.   The fixing device according to claim 4, wherein the resistance heating layer is formed by coating.   The fixing device according to claim 1, further comprising a rotation support member that supports a rotation state of the fixing member at an inner peripheral side of the fixing member and at least downstream of the nip portion. .   An image forming apparatus comprising the fixing device according to claim 1.